The question you may have meant to ask .... the answer is "depends".
If you have an unused win 7 pro retail licnece - then you can use it to load Win 7 pro on your PC
Even if you have used it before - you can still use it - as long as you ninstall it from previous installations/machines.
If your Win 7 pro licence is OEM - you can as well - as long as you have not used it before (if you have used before - its use is tied to the original PC you used it on).
Similarly - your old Win 7 home premium cant be used elsewhere if its OEM (as its tied to the PC)
If its retail - you could use it elsewhere
Does this help? If you can clarify what licences you have (OEM or retail) and if they been used before... we can prob hel pmore.