HDD problems?

[EnoVation]

a while ago i managed my first build. it worked fine for a while but for a few weeks now i hav been having some pretty f****** annoying problems. cannot pinpoint any specific time/cause, they just seem to occur at random
amd phenom x4
ocz reaper memory (2x2gb)
Gigabyte GA-MA78GM-S2H
Seagate ST3500320AS (2 running raid 0)
ATI radeon 3850
and windows xp pro sp3

i keep getting windows errors and at points the computer will turn off for no reason at all and will not turn on till power cable is unplugged and plugged back in.
errors are:

0x000000F4 (0x00000003, 0x8AA46020, 0x8AA46194, 0x805D297C)
and
0x0000007A (0xE1FEE930, 0xC000000E, 0xBF91D5A3, 0x802A1860)

removed graphics card problems still occured, tested ram as well, all seems fine. checked drivers for graphics card (which never had problems in old pc) and looked for HDD updates. installed s/ware from motherb disk. i kinda feel as though its a bad sector on HDD but im not sure if it would be hardware or software. any advice would be really appreciated
thanks

 

[EnoVation]

no overclock and dont see how any over heat could occur as im using a huge cpu cooler and case is open. tested ram by removing one stick at a time and seeing if problem still occured. http://www.ebuyer.com/product/141930 thats the ram. it says it needs 2.1 V but i dont know how to check/ test what im running to it. psu is win power atx-450