New Disk

I am running WinXP Pro, SP2, Have Vista on a DVD and have a DVD reader attached to the computer on a USB port. I have a replaceable drive unit where I can remove one hard drive and insert another very quickly. However, when I remove my WinXP Pro SP2 hard disk and place a new Western Digital, 160 Gig hard disk in the system as the primary hard drive with a secondary hard drive in place and the proper Jumper setting and I set my BIOS to boot from floppy and reboot the computer, the system recognizes the secondary hard disk as the C: drive and has no other drives assigned. Not sure what is wrong here but any help will be appreciated. Thanks in advance, Sid Kraft