G35-DS3L 8 gigs Memory; Windows 7; timing or voltage issue?

Hello,
I've been using 4 gigs (4x1) Corsair Twin2XC6400C4 memory (4-4-4-12; 2.1 volt, I think) with a Gigabyte P35-DS3L board running Windows 7 RC. It's been working great.

I had some extra 8 gigs (4x2) Corsair Twin2XC6400C5 (5-5-5-18; 1.8 volt) memory that I thought I would try. I installed it, but now when Windows 7 loads, it loads INCREDIBLY SLOWLY. It takes about 10 minutes to load windows and then it remains unusable.

Can somone point me in the direction of what might be going on here? Is it the voltage?

How can I corrett this situation?

Thanks very much for your help,
Mahlon

^That or it's more likely because your page file is 12-15GB! If you just left the pagefile alone it will automatically grow to 1.5*the amount of RAM installed. Reduce pagefile to 4GB or just turn it off. Also DL and run Memtest86+.Start by uping the voltage to 2v. Using 4 DIMMs usually need extra voltage.