You should check your RAM levels
This would only affect loading times, not fps. He has 2GB RAM anyway, so it's not the problem.
Keep in mind to turn off your browser
Won't do anything.
Change filtering to bilinear, and keep AA at at least 2x. Games are so ugly without AA.
I can't tell the difference. My recommendation would be to turn AA off and leave AF on whatever you want, because AA takes up a lot of processing power, but AF takes relatively little.
Use the steam .gcf defragger on all Source2007 games, and refresh TF2's local content.
If you do refresh local content (it won't do anything) do it
before defragging. Also, use GCFScape to defrag, not Steam.
The most important question is: what's your performance in episode 2? (compared to tf2)