Hi  I have a new laptop and a new desktop both running XP Pro.  When I
plug in my MP3 player or an external HDD the computer registers the
fact that they are there but neither of the computers will show either
MP3 or HDD as a new drive in explorer.  The little tray icon responds
and allows safe detachment of both but no go in order to access files
on either of the devices,  has anyone any suggestions please?

Right-click My Computer and click Manage.  Click Disk Management.  On
the right you'll see all of your drives that are connected and
recognized by Windows.  You might even see two with the same drive
letter.  Right-click the drive or MP3 player that's not showing up in
Explorer and click Change Drive Letter and Path. Change the drive
letter to one that's not in use and hasn't been used previously by
another device. For example, if you have two hard drives and two
CD/DVD drives and they're already in Explorer as drives C: D: E: and
F:, choose G: for your new drive. If it still doesn't show up in
Explorer, choose another one like H: or I: or J: or...you get the
idea.  Do this with each drive/MP3 player until they each have their
own drive letter and show up in Explorer.  It'll work...Merry
Christmas.

That should work, but if it doesn't try disconnecting all other USB
devices from your laptop/pc, turn of the pc then plug the new device
and turn it back on, if a conflict is the issue it should recognize
the new device. If there is a conflict with another you may be able to
resolve it by simply rearanging the order of pluging them in.