ok thanks I'll have an experiment or two, by the way i notice your version is quite different this is mine
Loop
{
  MouseGetPos,mx,my

  If (mx=0)
  {
    If tabbed=0
    {
      Send,{Alt Down}{Tab}
      SetTimer,TAB,800
    }
    tabbed=1
  }
  Else
  {
    If tabbed=1
    {
      SetTimer,TAB,Off
      Send,{Alt Up}
      tabbed=0
    }
  }
  Sleep,50
}     


TAB:

I find the idea very creative and the best I have tried so far. However in practice its not working so well!
I sometimes (quite often) bring up the gui when I dont want to - for instance when clicking the back button on Firefox. I guess I must move the mouse a little too far to the edge.
It would be great to  have the "hot" area smaller.  To Exclude the very top 2inches of your left screen and maybe the bottom too in case it interferes with clicking the start menu.
any hint how I could change the script in some way?

The first post is very outdated now, NOD32 for instance is at version 4+
as for resource usage that also changes per version. I left Kaspersky for nod because people said it was lower in memory usage but the version I tried (4.0) was not. so I guess it depends exactly what version you are comparing with what