VirtualDub is based on VfW (Video for Windows) and thus relies on VfW Codecs.
The entire idea behind VfW Codecs is to install the Codec
system-wide, so any VfW-based application (e.g. VirtualDub) is able to use it.
Just putting the DLL of the VfW Codec into VirtualDub's install folder won't work, because the Codec must be registered to the operating system.
If you are looking for something like VirtualDub, but
without the pain of having to rely on VfW, I highly recommend to you to give
Avidemux a try.
Avidemux ships with all the required required encoder/decoders "built-in", so you won't need to install anything else on the system.
Also the
ZIP package of Avidemux works "out of the box", so you can simply unzip to your home folder and it works. No Admin rights needed.
And if you don't mind using a command-line tool, use FFmpeg (or MEncoder), as suggested by Dark Shikari...