Windows XP Repair Only on Dell Dimension E510 PC

My client’s Dell Dimension E510 desktop has some problems which I believe can only be
solved by a repair of the Windows XP-SP2 OS.
I cannot do a full restore from the Dell CDs, because that will reformat the HDD and
data will be lost. Recovery Console does not
appear to be active. The system will not
boot into safe mode. The nature of the
problems are such that backup or copying of
critical data isn’t an option. Is there a
way to force a repair of the OS using the
Dell CDs? Has anyone had any success using
Reimage on Windows XP? Any help would be
very much appreciated.