I think this is a sign pat. The sign is, give up NS.

or 'install a different os'

Yea. See sublime, when you troll enough, even the computer doesn't like you?

that netgraph looks exactly like a wireless netgraph ;p but the conversation says ethernet cable :/. And sadly I can't for the life of me see anywhere the specified network card :P I'd assume all your shits up to date and it probably isn't the fresh install of windows (unless its wrongly configured lolwindows), atleast this narrows down the problems.
How bad is it on other engines? "seems ok the one time I played l4d2" is a bit weak to go on, if it's related to hl1 then again that makes things a lot narrower to trace; if it isn't and you can identify the problems in the other games aswell then we can switch to more general network troubleshooting ;/