USB Device Not Recognised

I am a new member and this is my first post.  I bought a DANE-ELEC 320 gb external hard drive (USB) and whilst it shows and works on my new Dell Studio 17 Laptop it cannot be seen on my three year old Dimension 9200 using Windows XP Professional.  I read the Dell support advice pages and updated the BIOS and Chipset to no avail.  If I navigate to Disc Management (via Admin Tools - Computer Management)  I can see the device listed and right clicking allows me to allocate it a drive letter (F) and I can then right click and open the device, see the contents, and drag and drop as usual.  However, the drive does not appear under My Computer or Windows Explorer.  I have to repeat the procedure every time to see the USB external hard drive.  Other USB devices such as Memory Sticks show OK although a memory stick lent me by a friend failed to show a couple of weeks back.  Again it was OK on the Laptop.  Any ideas?