When I tried starting up the game my mouse cursor turns into a red sign and then crashes.

Is this is a laptop? If so see the Laptop section near the end of the WOTR FAQ. Make sure your WOTR is updated. Make sure DirectX 9 has been installed as per section 4 (part 3).
Also see section 30 in the FAQ.
https://www.wingsoverthereich.com/index_htm_files/WOTR-FAQ.pdf

I'll move this to Technical sub forum soon.