I have a chinese gps system the problem with it for some reason it can not see a sd card anymore it just happened on day it was fine next it done this. I have tried many different cards and they are all the same they also can be read ok in my PC. My gps system is running wince5 if that helps everything else works ok can get into wince ok but it just will not see the sd card anyone got any ideas

Assuming you did not install anything that would mess with core WinCE files or drivers, the first suspect is always the SD Card--which you have already eliminated as (not) the problem.
The next suspect is, unfortunately, a hardware fault inside the device. Might be (if you are lucky) some dirt or debris inside the card slot--try blowing it out. If you are not lucky, the card reader has failed.