Some of the program files are encrypted, and use prefetch tricks as an anti-debugger measure to discourage people from looking at the code. Make sure you're using DOSBox 0.73 and set cputype=386_prefetch in the dosbox.conf file.

BTW, the game appears to be commercial software. If it's not been explicitly made available as freeware by the rights holder, it doesn't belong here.

Thanks thanks thanks 😊 now it works with dosbox+386prefetch, and it never worked except with my first pc, a IBM PS1 (386sx)
I'd like to understand why it's not working with these two machines: one is a pentium 200mmx and the other is a p4 3ghz ht, even in pure dos mode! I remember a friend of mine used to play it with no problems on a 286 cga machine too. does it use instructions not supported by pentium or newer machines?

And ... yeah ... I suspected it was not free so I removed the attachment (so geoff crammond is happy now 😎 )

The instructions are compatible even to modern x86 CPUs, but the prefetch queue (aka pipeline) characteristics like the size of the queue and various behaviors can differ between CPUs. Take for example the game JetFighter II, which also used prefetch exploits in its earlier versions; but the game developer later released patches (and new versions) that removed the prefetch exploits because the game wouldn't work on Pentiums. The stunt car game probably didn't receive support into the Pentium era, or it might have had a patch as well. I would guess that some hacker decrypted the code and removed the prefetch exploits for the warez copies on the net; thus a sort of unofficial patch.