You can easily install older version by using compatibility mode. Go to the exe (or setup) file and right click on it. From there you can go Properties and then click on the Compatibility tab. In the Compatibility Mode section, click the "Run this program in compatibility mode" box. From the drop down box choose Windows 7 (or XP...whichever).
I have install Sound Forge version 8 and Movie Studio (HD) version 11 on my Windows 8x64 machine. (Sound Forge took a little more work because it required .Net framework 1.1.) I wanted to paste a screen shot for the above instruction, but can't do it here.