Tekie,
Whilst I'm not in a position to offer you a solution or even a work around, I'm pretty sure the error codes and descriptions that are returned in your screen prints are actually XP error codes (or from the Microsoft operating system) rather than codes from Avast.
If you put a diskette into the drive which has some files on it, scan it, then take it out and retest with the removable media scan, you will probably like me get a different message and code than if you boot up and do the test without having used the drive.
I have a number of PC's that still have 3.5" disk drives, including P3, P4 and Core 2 Duo CPUs. The characteristics of the floppy drive is slightly different between all of them, whether this is mainly to do with the hardware, bios or software drivers I don't know, but on the P4 and Core 2, as well as a portable that all have XP and Avast5 Home installed, your original problem of the floppy being accessed when you open Windows Explorer doesn't occur.