"0" = "Completed successfully"
"2" = "Unsuccessful; not enough free space"
"3" = "The process was interrupted before completing"
"4" = "Unsuccessful; drive contains errors"
"5" = "Unsuccessful; error reading from drive"
"6" = "Unsuccessful; error writing to drive"
"9" = "Unsuccessful; not enough memory"
"10" = "Unsuccessful; the drive was invalid"
"15" = "Unsuccessful; disk was write-protected"
"26" = "Unsuccessful; could not access drive"
"105" = "Unsuccessful; drive was locked"
"106" = "Unsuccessful; could not access drive"
"108" = "Unsuccessful; could not access drive"
"109" = "Unsuccessful; 32-bit compression driver not installed"
"249" = "One or more drives could not be defragmented"
These may have additional 0's or 0x in front of them.
Please let me know if this doesn't answer your question.
Regards,
Rick Gouin, MCSE