Team Fortress 2 Problem

There may be other topics and threads out there with the same problem, but I need help now. I recently installed TF2 onto my computer again. A very suckish computer at that, but only temporarily, and I tried playing TF2 again. I have the BSoD sometimes and sometimes TF2 just closes and I am staring at my Desktop Page again. I seriously need help with this to play. A few other things, I THOUGHT I had 3 GB of RAM, but it came out that the 2 GB stick wasn't working for some forsaken reason. I was only running on a 1 GB stick. I am getting some new RAM and hopefully that would help. And finally, I noticed that while playing the game, a process is running, named hl2.exe, that takes an average of 335,000 K of memory. I was wondering if that had anything to do with paged pool memory and that if I installed more RAM would it give it more room and not crash? I'm not such a great computer expert, but I just need help. I would like to thank anyone in advance who submitted a reply to this.

no dxdiag log?

I would recommend trying a script just to see if that works, your computer may not have the capabilitites to run tf2. m0re's for example
 
http://www.gotfrag.com/tf2/forums/thread/398811/

 A dxdiag log would help some of the techies here figure out what is wrong. (I'm not a techie)

ok firstly refer to this thread http://www.teamfortress2fort.com/forums/t/Ifyouwanttogetyourproblemsolved-3864.aspx then post what it tells you to into this thread. (that being the dxdiag)