miguel, if you are practising with the HD before switching to the compactflash, then you probably are using more i/o than you will need for CF. A CF can be configured in a 8bit mode so that you can access the full 16bit i/o via a single 8bit port. the hi byte is read first and the low byte comes second. This means the CF can be fully accessed with only 2 ports of a 8051. 256MB storage is great!

Also, with a CF, you dont need to worry about CHS addressing (which you probably have with your small HD), they all seem to use LBA which simplifies matters considerably.

Good luck