Possibly corrupt/checksum does not match/hang on any disk

Hi,

I recently dug out an old computer that i gave up on a while ago. The problem originally was that the psu blew (i went for a cheap option). After replacing the psu for a far superior model windows 7 would load but the usb's would fail after 2 minutes and then the whole system would hang. I decided that the motherboard must be at fault so i swapped it for another of the same model. The result was that windows would no longer load saying 'the file header checksum does not match the computed cheksum' before loading windows. I tried to reinstall but i recieved the same error from the windows 7 dvd. I've swapped the hdd and dvd drive with no success. Also tried swapping the ram which stopped the above error but now the system just hangs as it loads the initial setup files from the install dvd after post.

I am running AMD phenom x4 black edition, gigabyte GA-MA78G-DS3H Rev.1, SATA HDD, IDE DVD-RW. The old RAM is kingston hyperx ddr2 1066mhz 2gb x2 and the "new" RAM is an old 1gb samsung ddr2 533mhz. Graphics are on-board

Thanks in advance

Matt