Are you using XP or Vista?
How much RAM do you have? (Right click My Computer and click Properties)
Have you just paid for a new McAfee key or are you using a trial. If you are using a trial I would recommend you Uninstall it and install Antivir Free which is a very good product and is recommended by PC Advisor Mag. If you have just paid for it I would recommend a RAM upgrade.
XP needs about 1GB of RAM to run McAfee smoothly.
Vista need about 2GB of RAM to run McAfee smoothly.
Hope this helps
Reply if you need anymore help
PCWiz
March 2009