I would suggest you go to the microsoft website and download the Antispy (beta) program. I have found that it works well at removing spyware, even thouigh I have a good firewall and antivirus, it still found adware on my system.
be careful though, u can destroy your system if ur not careful in how u use it. If unsure about what to do, then always choose "quarantine" when the scan finioshes and gives u a report on what nasty things are on your computer.
To speed up your computer, you should do lots of things:
1. Cleanup all of the cookies and plug-ins in the Internet Explorer.
2. Terminate unneeded programs on startup.To disable the startup programs, you can click "Start"--Run--Type in msconfig--Under the "startup" tab, you can choose the unwanted startup programs.
3.Detect and fix Windows registry errors.