postal2 skip doctor problem

I just recently acquired the game postal2 (box, book, everything).

It was really scratched up and it wouldn't work.

I used a disk resurfacer and fixed it but after doing that, it would install, but warn that I didn't have the original CD. It kept prompting to insert original CD.

I ended up having to download a "no cd patch" for it.

Anyone know why a disk resurfacer (skip doctor) would stop an original game from playing?

I know that if you just copy a disk, you'll get the same error....

The Copy Protection Mecanic got scratched and surfacer didn't fixed it the right way?