As I am understanding it, your computer doesn't even recognize that the iFP is connected?....... in that case, you have either (1) a faulty USB cable, or (2) a bugged USB port. One of the two needs fixing.
Also, is your player turned 'ON' before you plug it in? I assume it is, which it needs to be.
If your computer recognizes it, but it just needs the drivers...... Try
THIS PAGE. It has the drivers from iRiver.