Here's a small list of linux utilities I've used to repair computers:
Data Recovery:
TestDisk - fix and recover partition problems
PhotoRec - scan sectors for usable file headers
Foremost - scan sectors for usable file headers
ddrescue - forensically clone a drive that has big problems
dd_rhelp - a script for ddrescue that gathers readable data before going for the damaged stuff to save time
partimage - image a partition or drive using the MFT (file based backup)
ntfsundelete - undelete files emptied from the recycle bin in ntfs partitions
Malware Removal:
ESET Antivirus - awesome antivirus, linux version
Avira - another great antivirus
AVG - antivirus, doesn't remove files

Avast - antivirus
Diagnostic:
badblocks - scan a hard drive for bad blocks and determine if it is error free
smartctl - show smart data from hard drives
cpuburn - stress test by maxing the cpu
Other:
chntpwd - remove passwords from local windows accounts attached to the machine
gparted - configure partitions
Ubuntu Disk Utility - a nice utility that groups features to do with disk management