Beyond Good & Evil
Braid
Command & Conquer: Red Alert 2
Deus Ex
Grim Fandango
Half-Life/Half-Life 2
Heroes of Might & Magic III (better with a buddy)
Hitman 2 & 3
Machinarium (fairly simple adventure game, you might have grabbed recently off PS+. Can't remember when it was listed.)
Mafia (I never played the first one, but the second one was pretty good)
Max Payne/Max Payne 2
Myst (any of them, they're all great)
Psychonauts (says here it runs in 800x600 w/Medium Details)
Rayman (if you like platformers, which I don't remember if you do or not)
Red Faction 2
Serious Sam/Serious Sam 2
Shadowman
Star Trek/Star Wars (I'm sure at least one of those games are worthwhile playing, but I've never touched any of them)
Morrowind/Oblivion (sounds like there's a workaround to get Oblivion running)
The Sims (admit it, you love these games)
Worms Armageddon (best with buddy, but still fun by yourself in short bursts)
XIII
Also, a couple of DOS games that I liked that you might get a bit of enjoyment out of if you can find them (might take some tweaking to get them working properly, or at least running in DOSbox):
Raptor: Call of the Shadows (very accessible shmup)
Cyberdogs (top down futuristic "dungeon crawler")
The Incredible Machine (problem solving obstacle courses, essentially)
DOOM (you can never go wrong with DOOM, I don't even need to link to gameplay footage)
Hocus Pocus
Catacomb Abyss
Commander Keen
Those recommendations are heavily influenced by the style of games I like to play, so take 'em with a grain of salt. Also, see if Bastion would work on your PC -- it might, it might not, but it's a fantastic game if you can get it running.