Ya, as stated above the processor itself doesn't have a real bearing on whether or not the graphics card will work, but again, you would get much higher performance out of said card with a better cpu. The P4 would just hold the 8800 back, but would it work? Hell yes.
And on the salesman thing. I find some people are way to harsh on salesmen. I work at best buy and I see it all the time. People expect computer salesman to know Every answer to every single question. When your in the computer field, I dont care who you are, you are not going to be an expert in every single field. But what makes a salesman seem stupid or retarded is when they wont admit to not knowing something and they just rant on about something they dont know anything about.
Mind you, im 19 in college, working at Best Buy to take a look at the pc field from a sales perspective while I go to school. I actually learn a crapload of things every single day. I honestly never thought I would seeing how its a Best Buy (and when I used to go in there all the time the employees never seemed to know very much). But what many people dont realize is that you dont have to know anything about pc's to be hired in these departments at retail stores. They care more about how you handle customers and people. =)
stupid, but the way it works. But I try to be the most knowledgeable of the bunch at my store. =)