Originally posted by mcgrew
To be honest it doesn't usually matter what kind of monitor you have. Just choose Generic Monitor for the highest resolution you know it will support. Don't worry if you choose one too low, it won't hurt anything.
To be honest, it matters a lot what kind of monitor you have. And the HorizSync and VertRefresh part of the config file is the most important to getting the resolution correct, and those settings have everything to do with your monitor model. If the screen won't even display, your best bet, short of reinstalling Linux is to get ahold of a live CD (Knoppix, Mepis, whatever) and boot in and mount your already-installed partition. From there, you can edit the xorg.conf file.
As for how to get the live CD for recovery... you can use a friend's computer to burn an ISO of a live CD. Or you can go to the library and check out a book about Linux (Point-and-Click Linux has a Mepis CD in the back).
I found the horizontal and vertical ranges for my monitor at the manufacturer's website. You can probably find yours there, too.