Just call and reactivate.
If it is a legal copy you won't have any trouble.
On another note, Linux can be fun and rewarding but you need to know what you may be in for.
For one, Ubuntu is Linux. Actually is a distribution of Linux. There are hundreds out there but Ubuntu is one of the easiest to learn and most popular.
If you plan on gaming, Windows is by far the better choice for compatibility.
Sure, you can run a lot of games on Linux and most are free but most of the big name games out there won't run on Linux.
There is also a learning curve as far as installing programs onto Linux.
For the most part it is actually easier but it's still "different"
You can download and burn Ubuntu to a disk and boot to it. This is called a "Live CD"
It allows you to try before you install the OS. The entire OS runs off the CD without touching your hard drive.
Give it a whirl and see what you think of it first.
Thank you very much for the quick response. I'll get right into it. The copy is legal, but when I went to go activate it it said specifically that the key had exceeded the maximum number of activations blah blah. Compatibility is the biggest factor as far as switching goes as you've stated. But what about Ubuntu, does it have the compatibility issues like Linux? The difficulty installing programs on Linux as you said seems like it isn't worth it. One more questions. What is the difference between Linux and Ubuntu besides being a different distribution? Is it just simply a more user friendly OS?