Thanks for all the answers
I know my forum name is confusing. I began with an old GeForce card, but I have a friend who works with computers, and I have borrowed other cards from him. Currently, I am running one AMD Radeon HD 6700 series.
The driver is version 12.104.0.0, from the 13-4 installer. I have been switching drivers back and forth because I have been trying to mine on that card simultaneously with a 4850. No matter what I do, I couldn't get that to work, GUIMiner didn't start, it only got a tray icon that soon disappeared. With some drivers other programs crashed. As I said, I have spent at least six hours and twenty reboots on (not) getting it to work. I think I got all other drivers out before installing the one I just mentioned.
I think the problem lies in the drivers, if you search AMD.com, you will find that a 4000 series card don't use the same drivers as 6000 series card.
Mixing 5000, 6000, 7000 cards is ok because they use the same drivers.