A Drive Inaccessible

Having upgraded from ME to XP Home....

I now get the following message...

A:\ is not accessible.

Incorrect Function.

I appear to be able to 'format' a system disk, but I get
the message 'Unable to compete format' for a standard
disk...

However, if I attempt to 'see' what is on a disk, I get
the message as described above.... and it doesn't appear
to actually access the drive to determine whether it can
actually read the disk...

Any ideas?

Thanks in advance

Paul Cox