Just a week or two ago my motherboard got fried in my pre-built desktop that came with windows xp loaded on it. It had a 250gb sata 5200rpm hard drive in it and I wanted to take this out and put it in my new build so that I could save some money. I ordered windows 7 on a disc to go with my new build. I planned on trying to remove windows xp before I even got the new computer, so I hooked it up to another computer of mine and came across the problem that I need to register my xp with the computer I was trying to clean up the hard drive with(I know I'm a computer newbie). If I put this hard drive into the new computer with the xp still loaded on, is there anyway that I can get the computer to delete the xp and load windows 7 off of the disc without ever having a conflict between the two operating systems?
Putting an XP HDD on a modern motherboard will just give you BSODs. Just build the new machine and load Windows 7 fresh.
Once the new installation is done, then you can attach the HDD and either format it or if you want the data, just delete the Windows folder that has XP.
If you want to use the old drive as your new system drive, attach the drive, put your Windows 7 install disk in the DVD, and start it up (change the bios to AHCI if it isn't by default), and do a custom install, first unpartition all existing partitions and then let Windows 7 install to the single remaining unallocated space. Win 7 will clean everything out and install to the old drive.