Trouble With Trying To Play SMBX 1.4.5

[King Mario]

I have a problem trying to use SMBX 1.4.5. I'm using Windows 7 SP1 on Virtualbox, since my parents don't want me to play it on my host computer. Whenever I start it up, it shows that SMBX init has failed, and that turning off antivirus might fix it. However, the only antivirus material I had was Windows Defender; I turned it off, and it still doesn't work. Am I missing something important?