I have XP and it would not start at all. I am not using the original installation disk but my friends copy of it to repair. I typed in FIXMBR on the repair screen and the following message came up: "This computer appears to have a non-standard or invalid master boot record, FIXMBR may damage your partition if you proceed." Can I do this without losing documents and programs? What exactly are partition tables? Do I need the original disk? My computer is a Sony Vaio