USB Device would not showup as drive after install

Hey there everyone,

The problem I am experiencing is that my Win XP SP2 would not show me my external USB devices after I plug them in and install. I have my photo camera and mobile phone in mind. Before I reinstalled WIN, everything was fine, but after I put SP2 - problems appeared.
I used to see my camera and phone in the explorer with the assigned drive letter. I could browse them no probl. Now, I see that windows installs the device fine, but does not show it in the explorer as a drive.
What do I have to do to make the device appear in the explorer as a drive???

IMPORTANT TO KNOW: I have knocked out the Logical Disk Manager Service in the Administrative tools - after the windows failed to show me the new drives. The reason was that it kept refreshing my external USB HDD. Imagine that: I am in E:\Whatever_folder. Windows refreshes the connection and it throws me into Control Panel and acts as if the HDD was just plugged in... so I have to go to the E:\whatever_folder again. That would happen like every ~1 minute.

Thank you in advance!