HP Recovery Partition boot

I have been chasing around a problem with my mother in laws HP Pavillion.

It gives message that C: is "Corrupt and unreadable" It boots from the D: instead which is a Recovery Partition.

Obviously there is no install disk.

Chkdsk /f is not possible because the volume is in use.

Is there a way to do a system recovery of the C: when the C: won't boot?

If not, is it still possible to do a Recovery on the C: while running from the D:?

booting from safe mode produces a long list of system32 files and such but doesn't boot C: in safe mode.

Could I use fixboot or fixmbr commands in the recovery console? (I have a trial version XP install disk that has utilities on it).

I have never actually tried any of these things other than the chkdsk command because I don't want to cause any further damage.

For now she can use the computer because it boots to the D: and says it has low memory but she can still do the basics.

Thank You for any input anyone has.