|Can you be more specific on these 'backup files'? Are they selected files from a backup utility or just some files you've copied? |
If you know the name(s) of these backup files i'd just try searching for them. Maybe a tree /F /A > allfiles.txt from the command line c drive and searching the file ctrl+f for your file names.
Someone correct me if im wrong but my understanding is that a full hard drive wouldnt necessarily keep crashing your system. I would check for other things. Make sure you have the latest updates (service pack) and drivers for your vista box and that you are running virus/malware protection.