I've got F2 installed on a Vista machine, and when I try to start it, I get an error message that reads, "Fallout appears to be running in compatibility mode". And then, nothing happens.
I've got the Restoration Project mod installed, if that makes any difference. Also, I've tried running it in compatibility mode for a few different operating systems, and also as an administrator. Nothing works.
Any help would be greatly appreciated

Oh, I am an idiot. I should have thought to try that before.
Thanks.

Don't forget to mark Aliasalpha's post as a solution.

Did you try to turn off the compatibility mode? I had a same problem... and after a couple of tries (xp,98,2000 etc), I just turned it off and the game launched.

I would like to know on which OS you run Fallout2 with the patch.
I had the same problem running it on Windows7 and found a simple solution for my problem.

If you try to run it on Win7, then open the Fallout2.exe with a right click, go to the compatibility tab and check if any of the options is marked and fade in grey. This option will never change equal how often you activate or deactivate the comb-mode.
Below the "run as administrator" setting, you find a button for "change settings for all users". Go there and uncheck the grey fated setting and confirm with "OK".
Now the game starts!