Wierd CPU Spike issue

Hi guys,

Really weird issue.

I was running My PC with 6GB of Ram fine for a couple of days while i waited for my additional 6GB to arrive. It is the same brand, model ect. Ram.

I then installed the extra 6GB raising the total to 12GB of DDR3 1333Mhz Ram.

The First boot, took about 10 minutes. And I could barely use the system.

Literally, Start ups are taking 5-10 mins. I'm getting 300 hard faults per second about 30 seconds out of every minute (I've disabled Page file to no effect at all). I've also got CPU spikes, With know Process or Service taking responsibility.

I've googled my ass off all week and haven't found squat. My motherboard is a brand New MSI Eclipse (Supports Core i7 and up to 24GBs of Ram)

I just don't understand what could be causing this issue. It feels like I'm trying to run windows Vista of a machine with 12MB of Ram, not 12GB!

Any Ideas would be really appreciated.

[Edit]no idea how this ended up in Windows XP...