Well first off you probably shouldn't have paid for a $14 license since that was just pirated anyway (or sold illegally) but might as well try the upgrade and see if it works, if it doesn't, you could just fresh install and purchase a brand new key or arrrrgggggggggggggggg m8y. Theres not really any risk with just trying the upgrade to see if it will work.
I've seen stories of people contacting MS to try and transfer the key between comp's and had MS just delete the key and tell them to fuck off basically. Not sure how true that is but I've read a couple stories like that.