70 hours? That's nuts! It shouldn't take even 1 hour if it's a new machine. Sounds like something is wrong or that contradictory settings have been allowed to have equal standing and it interferes with itself. Check with the Microsoft Knowledge Base. Here's one possible problem "Drive's Contents Have Changed: Restarting" Message When You Use Disk Defragmenter. In short, be sure you turn off your anti-virus program before you do the defrag if this kind of thing happens.