FWIW, I recall from the widescreen and resfix threads that in fact it was not necessary to install the MS application compatibility kit. There was some contradiction in some of the threads. I have the resfix on and without the MSAC. Of course, there's a bit of stretching, but you learn to ignore it. Now, what I don['t know is how high you can go on the res and whether there's a limit. Mine runs on 1680x1050.
Here are some threads that I bookmarked quite a while back. Not necessarily on point, nor in any order, and possibly some are rather old or outdated, but may help you in searching for an answer.
http://www.subsim.com/radioroom/showthread.php?t=128723
http://www.subsim.com/radioroom/showthread.php?t=127054
http://www.subsim.com/radioroom/showthread.php?t=118002
http://www.subsim.com/radioroom/show...ght=widescreen
http://www.subsim.com/radioroom/showthread.php?t=137348
http://www.subsim.com/radioroom/show...ght=widescreen
http://www.subsim.com/radioroom/show...ght=widescreen
http://www.subsim.com/radioroom/show...ght=widescreen