Well, very late to the game, but I have cracked the "no sound" problem with MSP8 and Win7. I'm posting this for posterity, and on the off chance that it will help someone else. I, like many, loved MSP, having started using it back on version 5.
The following solution worked for me:
Presuming you have successfully loaded and run MSP8. I don't recall having too much trouble getting it installed to my Win7 machine, but it has been a few years. After some experimentation, I have found the problem lies with the uvavi.vio file, located in the "C:\Program Files (x86)\Ulead Systems\Ulead MediaStudio Pro 8.0\vio" folder. I happened to have Corel DVDMF7 installed, so I was swapping folders from it to the MSP8 folder. Narrowed it down to the Vio folder, and finally to the uvavi.vio file.
The version of the file that was installed with MSP8 is 356 KB (364,544 bytes) and has a date of Tuesday, September 06, 2005, 10:57:38 AM. Couldn't find a version for this file. The DVDMF7 file would give me sound while scrubbing and playing, but I lost the ability to create or use an avi timeline. It would only do mpeg. It also wouldn't render some audio. I tried a total of 5 different uvavi.vio files from various versions of MSP and DVDMF.
Long story short, I had an old DVDMF5 SE disk laying around that came with my Hauppauge card, so I installed the program and tried it's uvavi.vio file. It worked! This file is 356 KB (364,544 bytes) with a date of Tuesday, October 02, 2007, 3:14:16 PM. Note that it is exactly the same size as the one that installed with MSP8. The date is different. Scrubbing, playing, rendering to avi or mpeg, adjusting volume, etc. all work. So far I have successfully played wav, mp3, DV (PCM), and AC3 audio.
The DVDMF version that had the file that worked is listed as 5.78.0000.0 SE, when viewing the "about" screen from the program.
Good luck to any stragglers out there that miss MSP8. I wish Ulead/Corel had taken the time (3-4 hours) to do what I did.