laptop help

[Chickadee]

Help please guys.
Laptop running XP with service pack 2, avast, spybot and windows defender.
Over the last few days when turned on it turns on normally and then it stops completely for 3 minutes (yes exactly 3 minutes) - nothing works except the mouse. Nothing new has been installed.
I've checked and it's not running a virus scan so does anyone have any ideas what could be causing this please.
Thanks in advance.

[kujawski]

its the AI, your computer has a mind of its own and is having a think before deciding to go to windows.