E:\ is not accessible

I have tried 2 new portable flash card readers, neither work. I am getting error message: E:\ is not accessible incorrect function. Dell 4600C, xp sp2.
went to control panel, admin tools, computer management, disk management. My e drive does not appear. How can I use the flash cards and fix this?? Dell wants me to reset xp. too much stuff on this computer to back up. I have no other problems. My new nextel I870 phone needs the flash card for music. cannot use it until problem fixed. Help!!!