SCSI&IDE

Drive letters will change. The bios will always assign the first drive letters to IDE hard drives before SCSI. It doesn't mean you can't boot from the SCSI anymore (assuming the bios is set up appropriately). But some of the boot information I believe will get stashed onto the C drive as Windows just does that, which is no biggy (I think anyways). As for affecting the performance.. no. IDE is more of an interface, where SCSI is an actual separate bus all to it's own that's far more independant and they have certainly have very little influence on one another.