Jessica,
Although I am running Sony Vegas Pro 10 on a Windows 7 machine I too had problems with the manual install instructions the same as you did with your Sony Vegas Pro 11 on your Windows 8.1 machine.
After about a half and hour of trying to get it to work/install I was about to give up on it but decided it was not going to get the best of me.
Seeing that I used to teach computers to non-traditional students I am not afraid to try “off-the-wall” approaches to see what might work (it’s easy when it comes to manual installs. If one idea of mine doesn’t work – and many of them didn’t – I just went back and removed and/or renamed things that I did and tried another approach).
Lo and behold one of my “approaches” worked and now I have the Video Wall working for me (at least with my setup. Your mileage may vary but it’s worth a shot don’t ya think?)
Anyway, here’s what worked for me.
I created a folder in my main MY DOCUMENTS folder and called it Vegas Application Extensions. At first I named it Application Extensions but that didn’t work. I had to name it EXACTLY Vegas Application Extensions for it to work for me.
In this newly created folder I put in the DaviTools VideoWall.dll and the DaviTools VideoWall.png files.
I then opened Vegas and went to the VIEW menu and within EXTENSIONS Davitools VideoWall icon was there and it worked.
Like I said, even though you’re running SVP 11 on a Win 8.1 system the inner workings might be the same for you. There’s no guarantee that it WILL work for you and although the procedure I outlined above should not harm your system, if you do try it per the instructions above you do so at your on risk. I just had to mention that for legal purposes.
I wish you the best of luck and I hope it works out for you.
Happy Editing!!!