...uh why? It worked last night, and no changes have been made since then... as usual, I don't use the disk, but that's never been a problem before...

So I uninstalled two games I don't play anymore... yet still when I hit fallout 2 in my start menu it gives this error. Need help ASAP.

I've had that problem before a long time ago. I think I solved it by uninstalling Fallout 2 and removing everything left after the uninstall. I did copy my savefiles to a different folder so I could recover my savegames after reinstalling and patching the game again. I'm not sure, it's a long time ago, but I think it worked for me.

Try Salival's suggestion and after reinstalling, instead of using the start menu, try running the game directly from the folder using the .exe file. I bought a new copy of FO2 recently and found that it couldn't be run from the Start Menu shortcut. Might work for you.

Try running it from different paths, like from the CD 'Auto run', from a short cut on desktop, and then from the the installed folder (the exe file)

Has it got the latest patch installed?

Check my sig for it, and if none of that works, try asking at NMA, the link is also in my sig.