Windows 7: SD Card Drive question

I have a general question about how windows assigns drive letters. My son has a Dell laptop with Windows 7. First of all, the card reader works fine. However, I thought the drive letter was always fixed for the sd card reader. When he inserts a micro sd card and adapter in the slot, it pops up the windows info box with the header stating Secure Digital Card F:/. All is well. When he inserts a different micro sd card and adapter in the same slot, it pops up the info box with the header Secure Digital Card G:/. I don't understand the different drive letters. These are identical 2gb micro sd cards. The reason I ask is we are writing an application that stores the sd card drive in a local sqlite database upon initialization of the application. If the drive is not consistent it basically messes up our application. Any info on the multiple drive letters would be appreciated.

Was it immediately after you removed the last one, and did you eject the card first?

Welcome to Seven Forums jhound. Does the card reader show up in disk management (Start> In search box type Computer management> Enter> Click on disk management)? If so, you can assign it a drive letter. Then any card inserted should use that assigned letter. A Guy