Just for watching movies...
Radeon 7000 or 9200SE
Geforce MX4xxx or 5200

Yep, like he said.........for movies........great cards

Avoid the MX4000; many of them have crippled 32-bit (!) memory busses,
which wouldn't be much faster than your existing TNT2 M64. You don't
need a powerful GPU to play movies, but (relatively) fast video memory
couldn't hurt, especially if you run at higher screen resolutions.