GOG releases are generally fixed to run on all the operating systems listed on the gamecard and should generally run fine on modern hardware. I played GOG's Cossacks release earlier this year on a modern system running Windows 7 64 bit and it worked perfectly fine for me.

In some cases problems may still occur an specific configurations but they are usually solvable in one way or another. For example if Cossacks won't launch at all this patch should help. If a game won't work you can usually count on the community or support and there's always a money back guarantee if game won't work at all.