What I do when I hit a wall with install troubleshooting is to remove the HD from problem machine, install Win7 to it in another same-core machine with all other HD's unplugged, then return the HD to problem machine.
If Win7 will start, it will swap out all of the drivers in quite a show, requesting several restarts, but performance is fine on the dozen or so times I had to do this. It doesn't always work, but enough that it is worth the try.