What I basically did was a program that shows CPU/RAM/Sound levels in taskbar 
but it also shows in the alt+tab dialog

I have used this code snippet for hiding applications from the alt+tab
protected override CreateParams CreateParams
{
get
{
CreateParams cp = base.CreateParams;
cp.ExStyle |= 0x80;
return cp;
}
}
But that only works if ShowInTaskbar is set to false but I need it on because obvious reasons. Is there some way to make it not show in alt+tab and still preserve itself in the taskbar?