I don't know what format you are dealing with but usually NeroVison is a good tool to convert your files back to mpeg2.
NeroVison is included in the Nero CD burning package so it could be that you already have it.
Just run nerovison, create a new DVD project, load your video file into it and then press Export to create an mpeg2 file.
Then you should be able to import this mpeg2 file into Videostudio.
I have a Canon DC-100 MiniDVD Camcorder, and I normally record in VR format and edit it using Ulead Video Studio 11; however, I accidentally recorded something using the Video format, but Ulead doesn't recognize it, so I can't edit with it. I need advice on which program to use to convert it to VR so I can edit it in Ulead, which is the program I'm used to, or which program I can use to edit it in Video format as-is.