Q: When I try to compact the RTG Bills database, I get an error message that says Error compacting database . . . It may not be a database that your application recognizes, or the file may be corrupt.

A: Assuming that RTG Bills is working normally, the message is clearly erroneous.  The real explanation is that RTG Bills cannot compact the database because someone is using RTG Timer.  Have all RTG Timer users exit the program while you compact the RTG Bills database.