I recently purchased InstantCake for my recent Tivo Series 2 Standalone (TCD649xxx) unit. The software version is 7.3.1-oth-01-2-649.

 I'm ready to place an order for a hard drive and would like to know what size drive the Tivo and software version will support. Also, is there some "rule of thumb" to determine how many hours a particular size disk will hold?

Thanks for any and all help.