This is a contender for my personal "The strangest and most useless VOGONS posts 2007"-award.
There's no such thing as a "3D part of my videocard". Nowadays, all major functions of modern video adapters are implemented on one IC. Either the card works correctly (=the IC is OK), or it doesn't (=the IC is not OK). There's also some more additional potential for broken components on the card, but i won't go into details here.
If your card is broken, you should have mentioned that in your original post. One person actually wasted time answering to a problem that didn't exist in the form you described it in your original post. If the card is broken, then there's a high probability that you will have multiple problems, both in 3D (gaming) _and_ 2D (OS, applications, etc.). Assuming that DOSBox will run OK on a broken card, just because it's a "2D application" (which it isn't) is just very, very silly. Your answer to MiniMax' post implies that you knew there's something wrong with your hardware before you posted the original question.