Open CDE and go to Virtual Drives > Right Click > Mount
It should prompt you with a password and then go to MY Computer
You should see it now, if not go to the URL/Location Bar and Enter "G:" (Of course if CDE says its supposed to be "G:" Then it will direct you there, if needed to be formated Windows will prompt you.
If you are using Windows Vista please turn UAC off.
COMODO Disk Encryption requires administrator rights in order to mount/unmount vitual volumes. The virtual volume is not visible in windows explorer when UAC is on because when UAC is on, explorer.exe is running with limited permissions.