For DirectX PC games I use an old freeware version of "Fraps".
For old DOS games where PrintScreen do not work when run under Windows, I found ProgGrab (pgrab110) that seems to work fine (that's what I used for "The Need of Speed".
Advantage of these programs is that they save captures directly to bitmap files, so you can easily do lots of captures and sort them later.

Shall I post this info to that topic?