OK -- 35 GB is slightly on the small side, but is large enough. Ditto for the 2 GB RAM. And you're using the right graphics driver
I can't see that Vista SP2 and W7 RTM should really interfere with each other, and the fact that two separate setups, Pro and Ultimate, yielded the same poor results would suggest some sort of ... I dunno, drivers issue ?
I'm sure I've seen at least one report of raptors providing less than satisfactory performance in W7 (?)
Do you have a spare hard drive knocking about in a drawer, that you could perhaps use for a separate installation and see if it's a RAID-related problem ?
I see that your motherboard has a Gigabit LAN controller, that I have experienced issues with on my own mobo in W7 (causing severe instability) -- can you perhaps download the latest driver from their website, which solved a few problems on my own rig anyway ?