If you look at reviews for this otherwise nice, small A/C unit, you'll see lots of people complaining about a loud beep every time you press a button on the unit or the remote (e.g. changing fan speed or temperature). It's a high pitched, noisy, piercing, annoyingly loud beep, which wakes spouses and babies. I know of no way to disable or turn off this "feature". I looked for a wiring diagram and didn't find anything promising, so I decided to slightly disassemble the unit and hope to find a speaker. I wound up fixing it and here's how you can to!:

Tools required:

• Phillips screwdriver
• Flathead screwdriver
• Glue (I used a glue stick)

Time required: about 10-15 minutes

Skills required: Basic Handyman. Having said that, here's my disclaimer: Only skilled, certified electricians should attempt to fix electronic equipment. These units may contain capacitors which hold electric charge. Do not touch any of the electronics. I am absolutely not responsible for loss of property or person, damage to this unit or your cat, accuracy of these instructions, nor do I guarantee that this will even work. Opening this unit may void the warranty.

Steps:

1. UNPLUG THE UNIT!
2. Swing open the front vent like you're going to change/clean the filter and then gently and slowly swing open further to pop the two bottom hinges until it comes off. Set it and the filter aside.
   

   ( First swing open, then remove vent )

3. Remove 3 large screws and set aside (be careful not to brush anything up against the fragile aluminum vents).
   
   

   ( Location of the 3 screws to be removed for removal of outer plastic ring )

4. Remove 4 (there may only be 3) small screws around the control panel and set aside.
   
   

   ( Location of the 3 (or 4) small screws needed to remove the control panel )

5. Pop off the outer plastic front piece which has the top vents attached. Do this by gently inserting a flathead screwdriver from the inside into the slot about half-way down on the right side until that side comes off. Repeat for the left side. Then, the trick is to try and gently pull this outer plastic piece up (there are two tabs along the top like there were on each side). Be careful as there is a wire which attaches this piece to the rest of the unit, so orient it so that you don't put any tension on this wire.
   
   

   ( From along the inside, press tab with screwdriver to assist in removal of outer plastic ring )

   
   
   

   ( Set plastic ring gently aside -- there's a wire connected to it )

6. Remove 3 screws (there may only be 2) which were behind the control panel and set aside.
   
   

   ( 2 (or 3) screws to remove from electronics plate )

7. Lift slightly (there are two hooks along the right edge) and carefully pull out this plate with attached electronics only far enough so that you can see and can just access to the small, black cylinder (about the size of an Altoid mint). This is the PCB mounted speaker.
   
   

   ( View of the hole to plug with glue (looking down) )

8. Take your glue and make a small (about the size of a grain of rice) ball and place on the end of your flathead screwdriver.
9. Carefully use the screwdriver to apply the glue ball to fill the hole which is at the center of this piece (don't get glue on anything else). Be sure to pack enough in the hole to muffle the sound (about 2 grains of rice worth).
10. Now, carefully reassemble the unit in the reverse order.

NOTES:

• I would not test your success until you have at least the two electronic panels securely screwed back into place.
• For my two attempts at this, one left the beep barely audible and the other reduced the volume by half.
• I did all this while my units were installed in windows.
• If not obvious, this is basically irreversible.

Good Luck!

Edit, 05 June, 2010:
Wow, just wow, it's been 3 weeks and it still looks like that. Stay classy Microsoft.

I'm also a big fan of the open source Thunderbird email client. But there is one annoying thing using these two together: when you have a message selected and press 'delete', normally this sends the message to Thunderbird's trash (which completely removes it from Gmail), but in this case, you want to send it to Gmail's trash.

There was a configuration setting you could try, to send the message to [Gmail]/Trash, but Google doesn't recommend it (see 'UPDATE 2, Nov 8th' here). Instead you are supposed to move (e.g. drag-and-drop) the message to the [Gmail]/Trash folder manually.  Well, that's not too convenient when you have a lot of folders. So, what I've found is an add-on QuickFolders which will easily make a shortcut to that folder (and others) so that you can more easily drag-n-drop to send that message to gmail's 'Trash'.

Here are mine, and in case you're wondering, I have all these currently installed (Mac OS, is my current OS of choice) and Firefox runs at nearly the same speed as no add-ons:

--------- These are INDISPENSIBLE: ---------

DownloadStatusbar:  Simply a much better download manager.
http://downloadstatusbar.mozdev.org/

FlashBlock:  Replaces flash objects with a play button ('>') you must click before you can see it. Purpose is to lessen the amount of distracting things shown on most webpages.  You can add any website to a whitelist.
http://flashblock.mozdev.org/

NoScript:  Extra protection! You must explicitly opt-in to any javascript or java (and other plugins) for every website (permanently or for just this session). You can add any website to a whitelist.
http://noscript.net/

Tab Mix Plus:  Lots of fantastic tweaks for tabbed browsing.
http://tmp.garyr.net/  lastest (beta) versions here:
http://tmp.garyr.net/dev-builds/

Nuke Anything Enhanced:  Allows you to select any object (e.g. text, image) in a webpage and choose to remove it or remove everything else (can bring everything back with a simple page refresh).  Fantastic uses:  delete an annoying animated gif!, or clean up a page before printing!
https://addons.mozilla.org/en-US/firefox/addon/951

--------- Adds lots of convienience: ---------

MouseGestures:  Use your mouse for navigation. For example, holding the right mouse button while clicking the left, takes you back a page.
http://www.mousegestures.org/

LinkAlert:  Changes the cursor to indicate the target of a link (e.g. shows a small pdf image if it links to a pdf)
http://linkalert.googlepages.com/

ForecastFox: Displays the current weather (including radar/satellite) and forecast info constantly in your toolbar or statusbar. Nicely configurable.  Sure nice to have in a place where it actually rains!
http://users.rcn.com/shoofy/forecastfox_enhanced/

Fire.fm:  Brings last.fm audio streaming (free) to your browser with a handy small controller!!
http://sourceforge.net/projects/firefm/

Mac PDF: (Mac only) displays pdf documents in their own tab (instead of launching Mac's built-in "Preview")
http://code.google.com/p/firefox-mac-pdf/

GMarks:  Allows you to have access to your Google Bookmarks everywhere and easily.  I'm still getting use to this as I'm not a very organized bookmarker.  What's cool about this is that you can search for text within the entire webpage of any bookmark you have - pretty powerful that is!
https://addons.mozilla.org/en-US/firefox/addon/2888   see also
http://www.google.com/bookmarks/

BugMeNot:  Allows anonymous logins to those annoying "free" websites (e.g. NY Times)
http://erichamiter.com/firefox/bugmenot/

--------- KEY Webpage Development or Tweaking or Investigating Tools: ---------

Firebug: Tons of tools; can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page!
http://getfirebug.com/

Web Developer Toolbar:  Big and extremely helpful set of tools for messing with webpages.
http://chrispederick.com/work/web-developer/

TamperData:   View and modify HTTP/HTTPS headers, etc.
http://tamperdata.mozdev.org/

--------- Some 'niceties' provided by lifehacker.com: ---------
All these allow small tweaks to the way their respective websites are displayed:

better-youtube:
http://lifehacker.com/software/exclusive-lifehacker-download/better-youtube-firefox-extension-319925.php

better-google-reader:
http://lifehacker.com/software/exclusive-lifehacker-download/trick-out-google-reader-with-better-greader-262020.php

better gmail:
http://lifehacker.com/software/exclusive-lifehacker-download/better-gmail-2-firefox-extension-for-new-gmail-320618.php

better gcal:
http://lifehacker.com/software/exclusive-lifehacker-download/enhance-google-calendar-with-the-better-gcal-firefox-extension-260074.php

better amazon:
http://lifehacker.com/397946/better-amazon-firefox-extension-upgrades-amazoncom

--------- Deactivated mine, but you may want to check out: ---------

LiveHTTPHeaders: View HTTP headers of a page while browsing.
http://livehttpheaders.mozdev.org/

Nightly Tester Tools:  You'll need this to allow add-ons to work if you're using a beta version (i.e. Minefield) of Firefox.
http://www.oxymoronical.com/web/firefox/nightly

Google Pagerank Status:  Display the google pagerank for the currently viewed page. (VERY unfortunately, this add-on is not kept current)
http://www.tapouillo.com/firefox_extension/

This is an example call:

[s,w] = system([IMAGEMAGICK_PATH,'convert ',pwd,'/',outfile,'.png -rotate 90 ',pwd,'/',outfile,'.png']);

This is the error:

error:
dyld: Library not loaded: /opt/local/lib/libtiff.3.dylib
Referenced from: /opt/local/bin/convert
Reason: Incompatible library version: convert requires version 12.0.0 or later, but libtiff.3.dylib provides version 11.0.0

The work around is to replace the Matlab library with the ImageMagick one (only need to do this once and will stay until you upgrade Matlab):

cd /Applications/MATLAB74/bin/maci/   (or wherever your Matlab is installed)
mv libtiff.3.7.1.dylib  libtiff.3.7.1.dylib.MATLAB  (give it a different name)
ln -s /opt/local/lib/libtiff.3.dylib libtiff.3.7.1.dylib  (create a soft link to the Imagemagick library file)

EDIT: This is the much better way to handle this:

setenv('DYLD_LIBRARY_PATH',['/opt/local/lib/:' getenv('DYLD_LIBRARY_PATH')])

java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path thrown while loading gnu.io.RXTXCommDriver
??? Error using ==> serial.serial at 57
The serial port object is supported on the Solaris, 32-bit Windows and 32-bit Linux platforms only.

So, to get it successfully working, I downloaded these files: SerialComm.m, SerialComm.mexmac and SerialComm.mexmaci from http://svn.berlios.de/svnroot/repos/osxptb/stable/Psychtoolbox/PsychHardware/.

You can then use code like this:

PORT = 1;
% close (if previously open)
SerialComm( 'close', PORT)
% open
SerialComm('open',PORT,'9600,n,8,1')
% flush the buffers
SerialComm( 'purge', PORT)
% status
SerialComm( 'status', PORT)
% read
STR = SerialComm( 'readl', PORT);
% close
SerialComm( 'close', PORT)

[UPDATE 02 Apr, 2008]: Note, this same code didn't seem to work on a recently purchased Macbook. Good luck.

[UPDATE 27 Mar, 2009]: I see that in Matlab version 7.8.0 (R2009a) if you go to 'serial' in Help docs it now says for Mac OS X and Mac OS X 64 you can use serial('/dev/tty.KeySerial1'); I don't have a way of testing that right now, but it's possible that you don't need to use this third party toolkit anymore. If that's true, please leave a note here.