Is there any way to repack/modify/patch the .vpk files? To my knowledge GCFScape can only extract files from .vpk files. I also know that L4D has a vpk.exe but I don't have it and I don't know how to use it.

Nightgunner5 wrote:
Add -override_vpk to your launch options in Steam and it will read real files instead of files inside VPKs when possible.

Thanks for the info but it seems not to work... I'm not sure if the command works or not but it still doesn't load my gamemenu.res file. I guess that's not the correct way of editing Portal 2 menus.

Is modifying .VPK files illegal?

msleeper wrote:
I don't think modifying them is, but you can't redistribute copyrighted material - AKA, the Portal 2 content that is in them.

Ok, thanks for the info. That's just what I thought. I wasn't going to release modified .vpk files anyway.

By the way, can anyone help me here? How to create/modify such files?

Any ideas why -override_vpk is not working?