I have no idea if it's even possible to play on a modern machine, but this was my absolute favorite game for years after it released.
If you liked TA you should try Supreme Commander - made by some of the same people, similar gameplay (massive armies), and a bit more intricate plot
I bought the first one before I had a computer that could play it. intending to get an upgrade quickly. it ended up taking 6 years, and in the process I lost my copy. I know I'll love it. But I can't convince myself to buy it twice, lol.
I've heard the sequel is not so great, though.
I've heard that too but would definitely recommend rebuying the first one - I see it (and the xpac) on Steam for 5 or 8 dollars sometimes!