auto (usb) tethering when phone is connected? Can I somehow auto turn on 


usb tethering when I connect my
HTC Desire with Cyanogenmod 7.0.3 to my 
Windows 7 computer? 


NOTE Not when I connect it to anyother computer though.
If you use EasyTether, you can always have it enabled on your device and simply right click the icon in the tray (Windows) or enable it via terminal (Linux) and be on your way. Not quite 'default' but one click is pretty good. And EasyTether uses nothing when you're not attached to a computer, so no wasted battery or processing. It does display a notification icon to be persistent (not be killed), but you might be able to turn it off. 

As far as it knowing, you have to have the client installed, so any computer you hook it to that didn't both have the client and have you enable it computer-side would do nothing. 

Hope that helps!