I read a lot of posts that seem to have the same problem as me, but none of the solutions have worked yet.

I am using Vegas Movie Studio Platinum 8.0b.
My videos come from many sources, friends, downloaded raws, ripped dvds, but I'm having problems specifically with .AVI files. Vegas is only able to understand the audio, it says "Video: stream attributes could not be determined. So am unable to edited the video.

The videos will play in windows media, and I am able to edit them if I use Windows Movie Maker or Adobe Premier. I don't care for either of these programs which is why I wanted to try Vegas. I made sure the "ignore 3rd party codecs" box was uncheck in the prefences.

I got GSPot to check the codec, which said the video used Codec: WMV3 Name: WMP v9(VC-1 Simple/main) Status: Codecs are installed. But on the chance that I needed something else, I tried several of the different codec packs that were suggested in other threads(K Lite & several motionJPEG), but with them my videos wouldn't play as smoothly in my video players (along with not working with Vegas) so I went back to using Combined Community Codec Pack.
I've tried different DV codecs, including Panasonic, which also did not work. I followed the FAQ which didn't help either. I tried VirtualDub also. I really don't want to have to convert all my files, not only do I not want to lose quailty, but there are also over 100 of them. If there is ANYTHING you guys could suggest to help I would be so grateful!

And here's a screen of what it looks like when I tried to load one of my .AVI files...