Broadband Tweaks → Multiple Computers on LAN MTU/RWIN guidance

Hey guys I have a nice little home network with 3 machines on it, My main machine running windows XP SP2, my old machine given to my brother with windows 98, and a scrap machine I built from the left overs up my upgrades on my current machine using windows ME... Last I checked the diffrent OS use diffrent default MTU and RWIN. I was looking into tweaking my PC for faster results since I seem to be way below par on what I should get in my area for Road Runner Tampabay Brighthouse. Should be 5 down and I get stuff like 2.7 randomly in a blue moon I saw 4.6 once but never saw that again.

My question is if I try to change my settings and dont want to mess with the other PC's can there settings affect my speed or only there own? I have my MTU at 1500 now and also the router. the RWIN Is at some ungodly high number i think that I saw on a page to set it too that I think is reducing my speed. So just wanted to make sure before I try to tweak it the other machines wont give me false readings.

The tweaks only affect the box that is tweaked. Each one needs to be tweaked independently.