So one day I'm playing Borderlands, killing people left and right, and I decide to take a break. Next thing I know (as in next time running a game, give or take a few hour time period), all of my Steam games don't work at all. More specifically, it just flickers between the Valve logo and the menu (for TF2/CSS/L4D) and the opening credits just flicker and repeat for Borderlands. Now I'm not sure if I rebooted/turned off/slept my computer between these two points in time (of working and not-working), but I definitely did not install anything. Things worth noting: -OS: Windows 7 Ultimate (JUST installed on a spanking new 1TB HDD) -Hardware: EVGA 8800GTX, Intel Q6600 Quad Core, ASUS P5Q Pro Turbo mobo -Non-Steam games work perfectly fine (Mirror's Edge tested, assuming my other games work too; too lazy to install everything). -Installing new nVIDIA drivers doesn't fix it. -AVG and AdAware don't find anything wrong. -CCleaning in general and in registry doesn't fix it. -Removing my graphics card and replugging everything in doesn't fix it (this was before I tested other games lol) -Deleting Steam and all of my games, and proceeding to reinstall EVERYTHING doesn't fix it. -I'm typically a very neat computer user, so I have very little crap cluttering my computer. I don't want to have to wipe my HDD and start anew, since chances are I'll run into this problem again if I don't know what's wrong. I could TRY defragging tonight, but I doubt that would make a difference. Help would be greatly appreciated!