System resetting itself

I would like to firstly say hi to all of you.I've been reading the posts from a long time now, and they really helped.Recently I`ve bought a new computer...and the thing is that it just resets itself over and over again..with no apparent reasons..the configuration is , to make it short Amd athlon 64 3000+ , GeForce FX 5200 128 Mb on 128 bits, 512 ddr 400 dual channel, HD WD 80 giga 8Mb buffer, MB Asus A8V...o, and I have a rack too, which doesn't seem to work.Why does it reset itself?sometimes when within games,other times when on just plain background...and the games, such as Doom 3 or HL2 just give a lot of errors...i have all the latest drivers for the MB, video card..etc..and still..it resets itself..the Bios Date is 31 05 2005, therefore i don`t really think the Bios update is a problem...i need real and fast help...it would be most apreciated. Thanks

Have you checked if you are overheating? (Do you have any temperature monitor software installedd)?

Of course. The temp from the CPU is like 24-26 degrees Celsius and the system temps`s about 34-35 degrees Celsius.And in BIOS there`s no line which would tell the CPU to reset over a certain temperatur, like 35 :) I'm rather desperate..many suggested that the ASUS A8V with dual channel support is not that good ... and / or the fx 5200 is stupid. :/ still..why the reset and the whole bunch of errors in games ( aka Send to Microsoft / don`t send .. bla bla) and why won`t the wracj work ? :|