Slow Internet

Okay my computer is starting to get old I have a 2003 Toshiba with Microsoft Windows XP. I use Mozilla as a browser. My problem is in the last few weeks my internet speed has slowed dramatically compared to what it used to be. Every other computer in my house still runs at the same speed so I know it is just mine. I have run spybot and have avg virus protection that scans everyday. I deleted files from my temp folder and have deleted cookies. What else can I do to fix the problem? What is the problem? I am guessing spyware but I don't know. I would rather just be able to use free programs from the web if at all possible. Any help would be appreciated.

Thanks,

Ryan