I would suggest a few things to do.
Firstly, remember that ST:AT was released in 2001. So it was built on WinNT4/Win98.
First: Are you running DirectX 10? If so, that's 99% of your problem. That game was built around DX7. If you still have DX9.0c, then you may be able to get it running. Basically, DX8 is fully compatible with DX7. DX9 is so so compatible. But you have to "slow down" your system, and then still may have problems running it. DX 10, loses all DX7 and DX8 support in trade for the newer stuff it's designed to run.
Now, If your running DX10, forget running that game, and even Armada.
If you have DX9 still, go into your graphics control panel, and slow down the video card to a AGP 1X setting (if possible). Also, lower your sound card settings to slowest (no acceleration on either). And finally, if your system runs any "Enhancement" programs for sound or video, close those apps. And finally, if it's still freezing, remove the install, go through all these "slow down" steps again, then disable your Anti-virus and any anti-spam software, then reinstall it.
With any luck, you should be able to run the game. If not, find you a cheap secondary PC that runs a 1.2ghz with Win98se, 512mb ram, 128mb Ge-force video, with DX7 or DX8 already on it (I pick those up for about $50 - $150). I usually have to "upgrade them" to the specs I suggested for another $30 - $50. These may be old, but are perfect for those games you still want to play that MS has begun to force us to abandon