Are HP Windows 7 Licenses Proprietary?

My practice of scavenging has given me two (three if I can find the third) Windows 7 Home Premium licenses.  One is from a Toshiba laptop and the other two are from HP desktops. 

Can I use these licenses to load Windows 7 on any PC I want, or do I have to keep an HP mobo around?

You can't legally use OEM licenses on other hardware. I am not sure if it's possible at all.