If i decide that i want to uninstall windows 8 from my computer, can i then install it on another using the same product key that i used on the first or is it once used you cannot recover your product key?
........If i decide that i want to uninstall windows 8 from my computer...........
Based on the above partial sentence, I assume that your Win 8 is a retail version, not an OEM ( factory preinstalled ) version.
If I am correct on my assumption, then the answer is ...... yes, you can then install it on another using the same product key that you used on the first
Once you have uninstalled Win 8 from that computer, you have freed up the Win 8 product key. You can then use it to install on another computer.
For your information and future reference:
OEM version = the operating system is factory pre-installed in the computer. The OEM product key lives and dies with the hardware ( the computer.) It is not transferrable.
Retail version = the operating system (software) is bought separately from an retail store. It comes with an Installation DVD and a product key.
The product key can be used only one install at a time. One key, one install.
However, upon uninstalling, the product key is rendered legal to be used for next installation.