I TAKE NO RESPONSIBILITY FOR ANY DAMAGE WHAT SO EVER.
1. First you will need to download the patch:
Download UnDedPatch v. 3.33
2. Extract the .exe inside the archive to your Steam directory e.g. (C:\Program Files (x86)\Steam). Launch it and follow the steps.
If you want to disable the patch just delete the Steam.cfg or open it in any text editor and change the line from "BootStrapperInhibitAll=enable" to "BootStrapperInhibitAll=disable".