Are you trying to reinstall SP1 with 4 gigs of RAM?

On top of the BIOS update, you also need to install the KB929777 update.

In order to get into windows to do it, you'll need to remove some RAM (I drop down to 2 gigs) and then you'll be able to reinstall Vista. Once you've got Vista reinstalled, update using that patch and then restart.

Then, shut down your comp and add your previously removed RAM.

I recieved the BSOD for the better part of half a day because I was trying to install Vista Ultimate X64 initially with too much RAM.

Installing Vista is fun. It's like playing Tetris. But instead of lego-like blocks, you're using clay. And instead of Tetris, you're actually playing Jenga.