i have a problem that i might already know the answer to

in certian parts of certian maps i get all glitchy and only in that spot on the map...
i dont know if my intenet sucks or my computer sucks or there is a problem elsewhere...
please help
these are my specs
Amd Sempron 3000+ 1.81GHz
384mb ram

i dont know the video but its not old or bad
and my internet is wifi cable
please help
