I copy and pasted a folder onto the desktop. But about 10 seconds later the folder icon disappeared. When I tried to repeat the procedure it says I already have the folder on the desktop. When I look under Computer\C drive\Users\MyName\Desktop I see the missing folder(and the file is functional). Why can't I see the folder on my Desktop?

Logoff then Logonn or reboot, see if that makes any difference.

Also, right click on the Desktop, click on View and make sure Show Desktop icons is selected.