gwes.exe is not part of the SD content.
So it must be part oft the CE installation inside the DS708.
Try to boot without a SD and you should see the "no or invalid card...." message.
Try with a new SD card with only the base software on (no cars) which you can create even without the update period.
It should boot but you have no cars, but its fine for a boot test.
If the message still appears there is an error on the internal flash memory, filesystem of of the gwes.exe file.
All is not good and may indicate a bigger issue with your DS708.