Taking several minutes before I can use the computer

[Richard]

I'll try Strika, thanks.

Chillo: Yeah Hitman said that too, but I rather not have to backup all the stuff, so I'll try to fix it first.

Edit: Tried now, Strika. Nothing weird. 2 big ones: explorer.exe and Setpoint.exe, both fine.
Just before I could "use" my PC again, guard.exe suddenly took 99% of my CPU, after that it went down again. I googled it and it seems to be a part of AVG.