WD external HD shows on laptop but not desk top??

[AAnnoyeDD]

WD 120g usb hd is not being recognized by my desk top PC but is by my laptop.
Both are running windows 7.
Doesn't even show up in disk management on desk top.
I did change the drive letter using the laptop still no dice.

 

[aicom]

Does the HDD have an external power supply?

 

[AAnnoyeDD]

No it is USB2 powered. I tried using different usb ports too thinking that may be the problem. No such luck.