[I have re-booted uninstalled etc but to no avail.
Yet if I backup on another PC it works perfectly.]
My guess .... the main execute file is corrupt.
You say you have re-booted and uninstalled (the whole program?)
If you can, how about uninstalling once more with Control Panel's add/remove programs.
Run CClean click here including the 'Issues' section.
Install your OMWIN program again, and another reboot.