Mac Address Priority

[Peegee]

I thought this was sufficient but apparently not.

I want to set up one pc to download incessantly without lagging the entire home network. So I set up mac priority in my router (Linksys WRH54G)

Doesn't work - I'm lagged to no end and can't even play video games. So I put every stupid computer in my network except for my own on mac address priority lower than my computers.

Same deal.

I even tried changing the ethernet port priority but I think that only affects intranet traffic.

I asked my friend who told me that while he's not familiar with linksys routers, that mac address priority should do what I want. Am I missing something or not even looking in the right direction?