Hello Gregor, and welcome to Seven Forums.
That's what I was afraid of, and why I placed a warning in that post. His post has been removed now.
You might see if you may be able to do a system restore at boot
using a restore point dated before you did this to undo it.
If you did not have system protection on or do not have a restore point, then you might see if running a sfc /scannow command at boot
may be able to repair the system file.
Now for trying to get what is in the tutorial to work for you.
Do you have SP1 installed?
I've had others report that they were not able to some other tutorials here that involved Resource Hacker until they either installed SP1, or turned off a Windows Feature
(ex: Windows Gadget Platform), restart the computer, and turned back on the Windows Feature again.
Hope this helps,