how do I manually uninstall the sims medieval

I bought the game The Sims Medieval cheap online, and was really excited to play it when it arrived at my door. But my excitement was quickly lowered when I find out that I couldn't play it. When I installed both the game and the expansion pack "Pirates and Nobles", I had without worrying clicked "yes" when the game asked me to download the latest patch update. This resulted in that the game wouldn't launch when I opened it. When I clicked it again it said something about that the game was already running, when it clearly wasn't.

So I researched a bit online and found out that the patch update caused the problem. I had to uninstall the game and reinstall it afterwards. This time I should click "no" when the option to update was given for it to work on my computer (have Windows 8 btw). But I never got the opportunity to do so. Instead of getting the regular install screen when I inserted the disk in my drive, I got a error message saying: "The setup has detected that version 2.00.113 of the sims medieval is already installed. This setup installs an earlier version of The Sims Medieval (1.0.0). You will have to uninstall the previous version before installing this version".

Again I went online to find help, and a guy having the same problem got the answer that the game needed to be manually uninstalled for the updated version to completely disappear. I have no idea how to do that, but I really wanna play this game, so I hope someone can help me out. The person that posted this answer also said that one should only do that if they're really good with computers (which I'm not), and that one should look for help if they weren't capable of doing it. Where could I find that could do that for me?

So to sum up; I need to manually uninstall The Sims Medieval to play the game. Is it possible for me to do it on my own, and if so, how? If not, where can I get help. Thanks in advance.