Demo Tools

From HLAEwiki

The Half-Life Advanced Effects Demo Tools are a collection of tools integrated into the HLAE GUI for manipulating and fixing GoldSrc engine (Half-Life 1, Counter-Strike 1.6, ...) demos.

Those tools are standalone, meaning you don't need to have the game running in order to be able to use them.

You can access them from within the HLAE GUI form the menu: Menu -> Tools -> Demo Tools