Hello yoshi6601,
Please download the Windows Fix from the following link:
http://supermariobrosonline.tk/uploads/Windows_Vista_&_7_Fix.rarIt is a .RAR file, so you will need to download and install WinRAR in order to extract the file. Once extracted, you should have a folder called "Windows_Vista_&_7_Fix." Inside the folder is the Windows Fix file. Please right-click on it and select "Run as administrator" to run it and successfully install the Windows Fix.
If this does not work, please try downloading another fix via the following URL:
http://www.freemmorpgmaker.com/files/imagehost/pics/860b4da542e2fab0161aa303dfcc524e.exeSave the .EXE file to your computer and then run it as an administrator. Then, make sure you run the Super Mario Bros. Online Patcher to receive the latest updates. Once all of that is done, please see if you can run Super Mario Bros. Online.
I hope this helps!