That shouldnt matter.. You mean you get into actual windows, but its really slow... and 1 in 20 sucess rate? If it boots up only some times (like turns on) that could be a PSU issue.
So... your comp wasnt booting up with your old graphics card, so you bought a new one, and it still wont boot up?
If your comp was working before this new 3d card, then your PSU might not be able to handle it...or its a faulty 3d card.
I also found this: http://www.hardwareanalysis.com/content/topic/31874/
And another guy on another site said it was is USB 2.0 card causing it. He says to take out everything in your PCI-Slots and try.