rate 50000 (don't worry, this isn't overkill as most servers limit it anyway)
IF possible, try a wired connection.
I was having bad ass choke on my Windows 7 desktop and I have a pretty pro computer and can max it out fine, but it choked like hell on a wireless connection, even with over 90% signal and everything.
Using a wired connection gives me barely any choke on CS:S and TF2.
TF2 has some probs with wireless connections with causing ping fluctuation, i.e, choke, and it also runs on the source engine CS:S runs on.
Also, google "lower my ping" and check out some registry tutorials and see if any of those help.