I build my own machines and currently use XP Pro operating system with service pack 3 and all of the udpdates. It contains 2 identical 250Gig hard drives. I installed XP on the one HD and when Win 7 came out, I installed it on the second HD which gives me a dual boot screen at startup. I later built a new computer with Win 7 on it and would like to remove the Win 7 installation from the XP computer but more importantly, I want to get rid of the dual boot menu which is a hassle when I have to reboot and make sure that I select the earlier version of windows (XP) to boot to. I encountered this on another computer with the same setup and when I reformatted the HD with Win 7 on it, it hosed my boot up and I couldn't get Win XP to boot properly. I have tried to use some of the utilities that helps you to adjust your boot system but none of them seem to work when using 2 separate hard drives. They seem to be designed for partioned single HDs.
I hope I have made my situation clear and any insight you can give me would be very much appreciated.