Know one is going to close this thread unless someone grasses on us. 
If you have OEM version of Vista you will only be able to install on one computer or in your case a laptop, OEM windows is sort of like the disposable version of windows i.e. use once then throw it away. If you have the retail version you can install one version of it on any one machine at anyone time, i.e. if you latter decide to change your laptop you will have to uninstall Vista first before you can install it on another machine.

Originally Posted by
Erik
Sometimes you even need a new copy after a hardware upgrade.
It's a real pain.
I think the rule is (at least with Vista OWM) that you change any componant in your computer as long as it not the motherboard, as that is viewed as a brand new computer, however you don't get this problem if you buy a retial copy....or hack it, which is a no, no.