For example, if you have troubles with MP4, you have to download MP4 Splitter.
If with AVI - AVI Splitter.
If with VOB - DirectVobSub.
If with QuickTime - RoQ Splitter.
If with Matroska - Matroska Splitter.
If with RM - RealMedia Splitter.
If with FLV - FLV Splitter.
and so on.

How to install the splitter (for example, FLVSplitter.ax):
1) Unzip if it needed;
2) copy FLVSplitter.ax into windows\system32 folder;
3) Start -> Run...,
type
regsvr32 FLVSplitter.ax

Also you can type
regsvr32 path_to_FLV (where path_to_FLV is the path to FLVSplitter.ax)