Short answer: YOU.
I've run across, several times in the past, clients who expect their IT to maintain certain things for them such as license keys. This is a mistake. Firstly, license keys for things like Windows, Office, and whatever third party software the practice is using are the properly of the practice, not the IT support. Secondly, IT support comes and goes. Over the past two months, I've acquired two new clients from another IT provider. It happens. Now what if that IT provider had all the client's license keys and suddenly couldn't "find" them?
License keys cost a lot of money. Windows Server is around $1,500 a pop depending on how many Client Access Licensing (CALs) the key comes with.
Make certain you maintain your own keys. If you're ever in the position where you have to fire your IT support, you'll be glad you did. Nothing sucks more than to have to call an IT provider you told to take a hike and ask for a bunch of things you suddenly need to avoid buying it all over again.
JamesNT