Fix header of mpeg1 file ?

[prom3theus]

I have an old mpeg1 file captured a long time ago, and for whatever reason, it doesn't play correctly, won't edit in virtualdub, and I'm not sure how to fix it. The header doesn't seem to have any stream information in it at all. It's been a long time since I've converted most of my mpeg1 files to an mpeg4 format, and I actually don't have a single other mpeg1 file on my machine. Can anyone suggest how I can fix this? If I use a hex editor can I simply write in a header, and then use virtualdub to try to reconstruct the format of the file?
And what would the header look like?

Thanks