I used to promote this free antivirus and I still do for Windows Vista and more recent versions of Windows, but for XP Microsoft are using it to make life uncomfortable for XP users. Slowing the machine and popping up messages. XP users know their Operating System is no longer supported but they don’t want it sabotaged by Microsoft.
I recommend removal and install Avast Free antivirus or AVG Free. Both are quite adequate for the home user or even small business.