USB-HDs and sticks dosent show up in ?”my computer” on XP clients

Hello

I run a windows 2003 domain and have some trouble when users tries to use there USB-sticks and USB-harddrives in XP sp2.

1) When i log in as a admin the USB-sticks installs ” ready for use” and shows it self under “my computer”.

1) When i log as a user the sticks installs ” ready for use” and but it dont show it self in “my computer”. !!!

thanks for your help.