Turns out I have Access on another computer and it can read these (archaic) databases
These databases aren't as archaic as Windows itself! As I mentioned in my update on July 30th, Access and Jet are alive and VERY well. You should be able to use the Access Repair and Compress tool, then it will run just fine in Scheduler. If you notice, there are quite a few Stored Procedures in the database, as well as Referential Integrity links between tables. I use Access to maintain all of these. Access is the right tool for the job.