You will notice a difference a small bit in windows load times and installation times, and uninstall times, but nothing heavy. HOWEVER, if you get an SATAII drive, you WILL NOTICE a significant difference. nForce4 Ultra and SLi Deluxe supports that, which in fact are also PCI express. No, if you switch to SCSI HDDs, you WILL NOTICE A HUGE DIFFERENCE, but you better have a LOT of money.