Upgrade 802.11b devices to 802.11g.
First, run one program at a time on your computer. If that's not possible, run less.
A second way to insure that your computer continues running efficiently is by keeping your anti-viruses and anti-spyware up to date.
Third, check the programs that start-up when you log into your computer. You can find this information under the Start menu, and then by clicking on All Programs and then Startup.
A fourth tip to improve your computer's performance is to clean up your computer's registry.
Finally, upgrade the RAM (this is the memory of your computer).