Windows Crashing after psu failed

Hi i need a little help becuase im not sure where to start.story goes like this
plugged in my pc and pressed power button and my psu went pop. the computer wouldnt start so i replaced my psu with an ocz 700w gamexstream.
hardware list
asus a8n-e
amd 4400x2
1gb corsair twinx ddr ram
2x 160gb seagate sata hdd drives 7200.9
ati x1900xtx
acer al2216w screen
logitech g7 mouse
audigy 2 zs soundcard
ocz 700w gamexstream
with that installed i booted my pc up and lo and behold it worked.
only problem being it wouldnt load windows from the hard drive,so i had to use my xp cd and i managed to repair windows. i had to install internet explorer but that was about it everything else is fine.
but my pc keeps crashing,when i use an internet browser the mouse stops then my screen says no signal and i have to power off.sometimes when i power the pc up it hangs on the screen showing the hard drive capacity with loads of numbers and letters.
i probably havent gone into enough depth to recieve any help
i checked both hard drives with hdtune and it says no bad sectors on either of them. i relaxed the timings on my ram.i feel i may have to reinstall ati drivers.
oh also i installed a chipset driver becuase i hoped it would help the problem is there anyway to check that i installed it correctly?
the driver i installed was nforce4 x16 6.85
any help to guide me through finding the cause greatly appreciated
thanks
hugh

yeah i think that is what i will go through with,just a pain reinstalling office and all other software.but i can keep most files on my 2nd hard drive so it should be fine.still i will wait till exams are over before i reinstall windows

yeah i did,after the psu failed and was replaced when i powered up if came up with a hard drive error cant remember the exact wording,so i had to recover windows via the cd

yeah sorry i repaired windows via the cd