I have upgraded my wife's and my XP to 7. I have a 3rd computer running XP but it is corrupt. The 2 old XP discs are corrupt so I can't repair it. How do I obtain replacement discs. I am also considering doing dual boots for XP and 7 in the 2 other computers so that I can run incompatible programs on XP (such as BackUp MyPC to recover backups)