Q:
A: CAB files are setup files that may be needed for detect/repair of programs such as MS Office or Windows itself. While not 100% necessary, they'll come in useful if you have a problem. I'd recommend running CCleaner to remove leftover temporary files and other gunk first. If you still need more space, I would recommend trying to compress some infrequently used files (Windows' own Disk Cleanup will help with this) before you consider deleting CAB files.