Internet Lag

[PygmyBBQ]

Hey guys, I've got a slight problem with my latency as of lately. My internet has been really slow and I'm the only one on my network that is suffering.
As I'm writing this, with a 50 ping test to google my average is 175ms with a 24% packet loss. I've been pinging about 200-400 on world of warcraft as well.
Lately my ISP has had speed issues in my area, but that doesn't explain while I'm specifically getting the blunt of it and my housemates aren't being affected as much.
What should I do to diagnose my problem? =(

 

[JackMDS]

Assuming that you checked and cleaned your computer from Viruese and Spyware.

Try this, Optimizing the TCP/IP Stack - http://www.ezlan.net/Internet_Speed.html

 

[PygmyBBQ]

I optimized the TCP/IP stack, no change in the lag.
I also did a speed test to Los Angeles, which is 80 miles from my location. The download and rates are fine at 574/594 kb/s respectively, but my ping is 97ms.
Also, I forgot to mention that I'm wired into the router, so not a wireless problem.

Edit: My other room-mates are lagging as well. It seems like the first person using the bandwidth is lagging the least while the rest of us aren't getting as much? Is it possible that the router is giving priority to whoever was using bandwidth first?