USB pen drive detected butdoesn’t show up in MyComputer

This problem occurs mainly
when windows XP fails to
allocate a drive letter to your
portable drive(pen drive). It
occurs mostly with new pen
drives connected to your computer for the first time. If
you face such problem then it
may not be the pen drive’s
fault, rather it may be
windows trouble.
Fix:

You can fix this issue by
following some simple steps
given below.
1. Click Start, click Run, type compmgmt.msc, and then click OK.
2. In the console tree, click Disk Management. The Disk Management window will
appear.
3. On this disk management
window, you can see some
drives including the portable
drive. Right click on your
portable drive and click change drive letter and paths.
4. Now a assign a new drive
letter which is not being used
by any of your drives in My Computer.
5. After assigning the new
drive letter your portable drive
will show up in my computer
with other drives

If that does not work then use the second method

Method 2:
If none of your USB devices
detect ,this could be due to
wrong registry entries. i.e you
need to delete UpperFilters and the LowerFilters registry values. Follow the procedure listed
below to correct your registry:
1. Open Start >> Run, and type "regedit" (without double
quotes), and click OK.
2. Locate UpperFilters registry value. it resides in the
following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM
\CurrentControlSet\Control
\Class\{4D36E980-E325-11CE-
BFC1-08002BE10318}
3. Click on Edit menu, and select Delete and click OK. Note: If you receive an error when you try to delete the
registry subkey, you may not
have correct permissions to
edit the subkey.
4. Locate LowerFilters registry value. It resides in the
following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM
\CurrentControlSet\Control
\Class\{4D36E967-E325-11CE-
BFC1-08002BE10318}
5. Click on Edit menu, and select Delete and click OK. 6. Exit Registry Editor and
restart your system.

Thats all!!!