Battlefield 1942 not running

It looks like Microsoft introduced a sort of DRM blocker that has been interfering with people who play PC games with old retail discs. Since you said you are using a physical disc, I have found a few possible solutions for you.

Here are a couple specifically for Windows 7:

There are several methods to get around this on Win 7:

  1. Uninstall two Windows 'Security Updates' - KB2919355 & 3086255 - and stop using automatic Windows Updates so you can block these updates (hiding them may work for now, but they may sneak back) from installing when you do updates in future.
  2. Leave the update and use noCD fixes/hacks for any game that gets blocked.