Is it ok to just upgrade the previous (WinX) OS, or should I do a clean install on a freshly formatted HDD? Also, can you install the XP Pro upgrade version on a new system, i.e. no OS installed on the system? I did install XP on a spare HDD to check it out and after formatting the drive with my disk utility, but it will not install in DOS mode. I didn't try booting to the install CD, does that work?