Adblock installiert sich nicht..

If you login in Chrome -> logout.
Go to %AppData\Local\Google\Chrome\User Data\Default\Extensions and delete extension folder
Go to %AppData\Local\Google\Chrome\User Data\Default\Local
Extension Settings and delete extension folder
Restart Chrome
Sign in
...Done!

The default location for all Chrome extensions is

C:\Users\<username>\AppData\Local\Google\Chrome\User Data\Default\Extensions

When you navigate there, you'll find that all the folder names are cryptic, so you'll have to isolate the particular extension either by Date Modified, or by clicking in each folder and comparing the version number to the version number of the extension (find via the extension's page on Chrome Store).

To remove the extension just delete the particular folder, and restart Chrome.