SATA drivers not being loaded properly perhaps? Could be a BIOS setting not playing nice with the install. Disable ACHI in BIOS... With XP and Vista I would get a BSOD on installation if the ACHI drivers weren't slipstreamed correctly. In Vista it lagged on expansion just like yours but I'm sure it was because of the chipset I have, ICH9M-E/M. Do you have a spare HDD available?
UPDATE: i went to the store and bought a cheap 2gb of ram and replaced the 4gb i had and it worked win7 installed like a charm, apprently the ram is bad T.T, will have to find a way to send it bak to the US since i live in the carribean.... thanks for all the replys guys <33
I assume its SATA 1T HD. what mode you set your HD to ? AHCI or IDE ? if your MB has this option set it to AHCI! I have exactly this issue installing Vista and W 7. after set it to AHCi viola. hope your problem is the same as mine!