How to prevent installation of Google Chrome extensions

You can do this with a GPO. Go to Computer Configuration > Administrative Templates > Google > Google Chrome. Look for a folder named Allowed extensions. There configure a blacklist of *. This will prevent users from installing plugins.

I was going to add this as a comment to Lucas Kauffman's answer, but I don't have the rep to leave comments yet.

In Win7 Ultimate (and probably most other versions of Win7), you have to download and install Google's GPO manually before you have access to the GPO settings Lucas Kauffman mentioned.

DL: http://dl.google.com/dl/edgedl/chrome/policy/policy_templates.zip

DL and unzip google's Administrative templates, Then add the GPO template for Google Chrome manually: Right-click Administrative Templates and select Add/Remove Templates then browse to where you Downloaded and Extracted the policies and add the one for your region, then follow Lucas Kauffman's instructions:

"Go to Computer Configuration > Administrative Templates > Google > Google Chrome. Look for a folder named Allowed extensions. There configure a blacklist of *. This will prevent users from installing plugins." - Lucas Kauffman

you can make it local by giving permission on extention folder in this path

C:\Users\*your user*\AppData\Local\Google\Chrome\User Data\Default\Extensions

rightclick->security-> select user-> deny all