Leatek vs Zotac

The actual thing is i have an pentium 4 and gt 520(Leadtek) and when i play black ops i get 25+fps and when i watch an gameplay of cod black ops on gt 520(Zotac) they got 35+ Fps how should i get the same fps as them they have dual core 3.06Ghz and i have pentium 4 is this the problem or i have leadtek brand and they have zotac or this is the problem