It might work,btu for the full experiance I realy suggest at getting a better card and more ram. I used to play halo like you then I got another stick of 256 and a new (damn cant remember name) card and its been so much faster/clearer/cooler/better...
I assume that it probably will work...but if you are going to get a new video card make sure that you have an AGP slot first. And as kobaj said, get more ram...it makes a hell of a difference to go from 256 to 512 or even 1gig