I was having the same types of problems. I'am running 500GB Raid0 with a partition running Vista64 and Windows 7.
Windows 7 was completely unstable for me using the same bios settings, or so it seemed. Crashing when moving files,watching movies,gaming,downloading things. Moving large files accross the LAN always crashed once before it went through.
I was stumped because Vista was 12 hours+ Prime stable on the same system and had no such problems. I ran Prime95 on Windows 7 and it was still stable.
What fixed this problem for me was moving up the MCP,FSB and Ram voltage just a notch each in bios. It was the last thing I tried but it should have been the first. Not a single problem since doing that and I have been moving files watching two HD movies and gaming just to make sure. 48 hours on time and zero problems. Hope this helps someone because it worked for me.