Uncompress the files from pdvcodec.rar archive, right-click on the PANADV.INF file and select Install.
You may encounter a prompt saying: "The software you are installing for this hardware... has not passed Windows Logo testing..."; click on the Continue Anyway button.
You should now be able to load DV-AVI Type-2 files with VirtualDub (and any other program that loads AVI files).