I have an AMD 64 3500+, Asus A8v deluxe mobo, 2x 512mb ddr pc3200 generic ram, connect 3d Radeon 9800 pro, Antec 480w truepower psu, sata seagate baraccuda 200gb hd, o.s windows xp with service pack.
The problem i am having is my computer keeps reebooting randomly, ive checked the power coming from the psu, tested graphics card, run memtest for the ram, run a torcher test on the cpu, changed cables, updated drivers, tested for corruptions in the hdd, uni/reinstalled windows, but its still rebooting can anyone please please help.

You can turn off the feature that instructs XP to autostart on system
failure. Right click on My Computer and select Properties->Advanced
Tab->Startup & Recovery section->Settings button->uncheck "Automatically
restart" Apply. This will give you a blue screen with info on it and you
will have to manually restart the computer. The info might give you an idea
whether or not the problem is hardware or software related.

What service pack have you got?...SP 2? when you reinstalled windows did you reformat the hard drive?.. have you a virus on the PC?.what anti virus and firewall are you using?.how long ago did all this start?