it works with dial up, but don't choose games/maps that have alot of people because you (and everyone else) will lag thus booting you or they will simply leave.
i recommend you buy the game(cuz its really cheap now) and there is another halo called halo CE(custom edition, which is different from combat evolved) and it is free but you need the disc and serial code to play it.(i dont think there are cracks for it).
not alot of people play halo now because of other games (halo 2, call of duty 4, etc which are all available for pc) so i guess you really shouldnt worry about your internet speed but rather if there are any people playing this game anymore.
and dude, its 21 century, get cable or dsl.