Defrag Problem??

I am not exactly sure what comes first here, but here goes.

I have had 6 customers experience a situation where updates download but no
longer install. after trying all of the normal fixes for this problem to no
avail, I attempted to do a restore at which time an error said that restore
could not be done due to disc errors, when I tried to run chkdsk it would not
run.

When I tried to run defrag, it said it was running but nothing was
happening, I pulled the drive, added it to one of my bench machines, did the
repair, found the drive to be seriously fragmented, after fixing and
defraging returned to original machine, machine runs normally, still cannot
install updates, all of the restore points are gone. when I try to do a
repair of Vista, it tells me it is unable must do a new install.

like I said, I have had 6 of these so far and just talked to another
customer with the same problem,

Anybody got any ideas???!!!!!!!