File/Library/Backup.
Ideally put the media files back in the same location after the install - if their paths change you can fix this in the M library by doing a "Rename, Move and Copy Files" operation and choosing "Update database to point to new location (no file rename, move)", then choosing Find and Replace and changing the older location ot the new. e.g. c:\media becomes f:\media or whatever - as long as all paths changed in the same way.
Your settings will not be backed up - that, the is stuff under Tools->Options - so you might want to review what you've done and take screenshots of anything significant, for recreation later.
Ditto plugin settings, if any (I think)
