Camera card drive letters missing in Windows explorer

Been using Transferer to move photos from my cameras via USB to my computer (64-bit Windows 7 Home Premium SP1), but Transferer stopped working suddenly because it requires drive letters for the camera cards, which no longer appear in Windows Explorer, which does show the cameras listed as drives but without drive letters. I can transfer photos manually. My cameras don't seem to have a mass storage mode.

I'd be very grateful for any insight into what happened to the drive letters.

Thanks,
Steve

I realize I'll have to do a repair install, but I can't uninstall SP1.

Use this has a sp1 ISO

Download Windows 7 Integrated With SP1 ISO – Official Direct Download Links

Many thanks, helpifIcan.

I'll give the ISO a try. Earlier I uninstalled SP1 using wusa.exe /uninstall /Kb: 976932, which appeared to work. Two subsequent attempts at repair install (with firewall and antivirus off) failed at the end of the last stage.

Above post contains suspicious "antivirus" link.

You need to scroll down the ISO links come from digital river which is a M$ supported site.

"The upgrade was not successful." Now looking for way to retain settings etc. for clean install.