I never used Magic World, but I have used Matedit. If you haven't downloaded the lastest version of Matedit, you should it faster and alot of bugs have been taking care of, but Matedit Pro I think should be coming out soon. Anyways back on to Magic World, you may want to check your "C:\Program Files\" directory. Look for a folder called "Magic World" or something of that sort. Then, see if there's a .exe file in there and try running it. If that doesn't work then try downloading it again, but save it to your desktop so you can see all the files on your desktop. If that doesn't work then just wait a few days and try again

.
Edit: By the way you don't have to use a editor, you can just code your level using DB, if you want to I can show you how

.