Sorry dude, but it if you're just around 70-80 fps in CS 1.6 it means your computer can't handle more.
It's not like the internet has any impact on your fps - in fact, even if you'd be on a 56k dialup you'd have decent framerates all the time, if your computer could handle it, it'd just be laggy as hell.
Try to lower any significant settings and maybe your Direct X level, too. In the TF2 forums there should be a thread about getting it to run better on older systems - this should help you with all your orange box games (and GE: S) as well.
Other than that: did you defrag your HDD and your Steam games as well, recently? If the files are scattered around too much this could also be a part of your problem. Try to update your graphics drivers, while you're on it.