If the files are extremely important then I would buy a new laptop HD and clone the existing one to the new HD.Todo Backup
would do the job.
Download Todo Backup on a working computer and use the option to build a bootable CD.
Then boot from the CD on the laptop with the new HD connected by USB using something like this adapter
Use the clone disk option in Todo to copy the entire laptop drive to the new HD.
This would give you a complete copy of the HD to work with. You could then troubleshoot the Vista startup problem or give it to a tech to work on and know you have a safe backup copy. If worse comes to worse and a restore to factory defaults becomes necessary you still have a complete copy of all your wife's files for recovery. (You could troubleshoot the copy if that would make you feel safer)
At about $100 (HD and adapter) it is probably worth the investment to be on the safe side. You could accomplish the same thing without the adapter if you had a PC that would recognize both the old laptop drive and a new one at the same time and boot from the CD.