When troubleshooting driver problems in Windows XP, one of the
first places you may look is Device Manager, which provides detailed
information about every piece of installed system hardware.
However, with devices such as removable USB drives, you may need
information about devices that are not currently connected;
Device Manager recognizes these as nonpresent devices.
Here’s how to get information about those devices:

1. Go to Start, right-click My Computer, and select Properties.
2. In the System Properties dialog box, select the Advanced tab and click the Environment Variables button.
3. In the Environment Variables dialog box, locate the System Variables panel and click New.
4. In the New System Variable dialog box, type DEVMGR_SHOW_NONPRESENT_DEVICES in the Variable Name text box and type 1 in the Variable Value text box.
5. Click OK twice.
6. To view the nonpresent devices, go to Start, right-click My Computer, and select Manage.
7. Click Device Manager, pull down the View menu, and select Show Hidden Devices.
8. Note: This tip applies to both Windows XP Home and Windows XP Professional.