Uninstall them. Go to Control Panel, Add or Remove Programs, and uninstall them. Now, I hope you're not going to uninstall important programs such as firewall and anti-virus.
I also suggest you use Task Manager to see how many processes you have running at various times and whether any of them are obviously hogging CPU resources.
Have you experienced some degradation in performance? Are you currently using some spyware removal tools to keep your system clean? Ever used CCleaner? Do you ever defragment your hard drive?