BF2S Forums PC crashes when I try to play DoD:S and TF2

Sounds like a driver issue.

Does the computer automatically restart? Make sure you disable automatic restarts in case of serious computer error (it's a tick box found under the Properties of 'My Computer' somewhere, differs depending on what OS version you use)- so that when the error does occur, you can see the BSOD or error message.

Try the usual culprits: display drivers, sound drivers, plus any background-services that may be running whilst you play the game and conflicting.

If that fails, I'd suggest running a memtest on your RAM overnight.

Memtest is usually a utility you save to a floppy or a CD and then boot from before the computer finishes POST. In other words, before Windows or anything boots up, a memtest runs a rudimentary basic 'stress test' on all the channels of your RAM. Search Google for it, you can find downloadable versions that format to floppies and all sorts of other formats.

If the game does just freeze and lock up, and you are unable to exit with Ctrl+Alt+Del or the like, then it may well be a driver issue causing system crashes. If you have an Nvidia card, it is common for Nvidia drivers to cause problems with Vista 64... I think I read somewhere that almost 30% of Vista crashes are caused by Nvidia alone (I also run Nvidia and Vista, and experience intermittent problems at times). I would firstly advise reinstalling Steam and all of the Steam programs, just to rule out an application error with Steam / the Source engine. Then look into your drivers/firmware/software, and then lastly look at your actual hardware configuration and OS-- it's a good order of priority to approach problems with.