I recently bought a new computer with built-in memory card reader slots.
Prior to this I used to connect my digital camera with a USB lead, and Win XP recognised it as a Removable Disk in the normal way.
Now, when I insert the camera's Compact Flash memory card into the new computer's card reader, Windows recognises it as no less than four new Removable Disks. One of them allows me to access my pictures normally. If I click on any of the other three, a popup window asks me to insert a disk into the drive.