PAF can be most easily downloaded from the homepage at www.familysearch.org (lower right-hand corner of the screen)
Do you have a recent backup that works? (You can NEVER have too many backups.)
Can you export a gedcom file from your damaged database?
If you can export a gedcom, you are free to download PAF, create a new (empty) PAF database and then import your gedcom file. AFT is no longer available from its supplier. PAF is a very similar program. You will be able to work efficiently in PAF almost immediately.