Will a TV Tuner Card work with my Celeron?

I am running an ancient HP705 with a single core Celeron 2.56. Most of the TV tuner cards, like the Hauppauge's and ATI's, require a P4 or higher, but my smiling salesman says I can get away with it as long as I allocate sufficient video memory? Who is correct? At this stage a new computer is not an option until I pay pay some more pressing bills.