1) Make a backup of everything on the machine, "as is"
2) Verify to be sure it is readable.
3) Take that backup off-site.
4) Make another backup, just for good measure.
5) Install a named instance of SQL 7.0
6) Detach a user database (one at a time) from the unnamed instance of 7.0
7) Attach the database files to the named instance
8) Repeat 6-7 as needed
9) Remove the unnamed instance of 7.0
10) Install an unnamed instance of SQL-2000.