recommended antivirus software

I have four desltops and one laptop on my home LAN. Two of the desktops are employer provided and have McAfee antivirus software installed with a perpetual license. They seem to be working well without slowing me down so much that I notice. I recently bought McAfee Virus Scan Plus for my personal desktop. After installation, my machine was virtually paralyzed. I requested a refund. I’ve also dealt with Symantec and Kaspersky and wasn’t inpressed. Do any of you computer gurus have a suggestion for an antivirus software that works and doesn’t use a lot of computer resources? I’m running Windows XP Pro on all machines.