Where does Chrome store add-on extensions?

Once an add-on extension is installed in Google Chrome browser, you can view the the Extensions Files (the installation files) in the following directory in Windows:

C:\Documents and Settings\*UserName*\Local Settings\Application Data\Google\Chrome\User Data\Default\Extensions

If you can't find the files there, you have to first type chrome://version/ in a tab and then look out for Profile path inside that and after you reach to your profile path look for Extensions folder in it and then folder with the desired extension Id.