installer brings an error and does not allow installing or deleting extensions,
you can solve this problem the following way:
Delete the inventory.xml
file from the folder with extensions. The file should be located by the path
similar to C:\Program Files (x86)\Perpetuum Software\Perpetuum Soft Rendering
try to run the installer again.
If this does not help, please try to install extensions manually following the instructions of this article: http://helpcenter.perpetuumsoft.com/KB/a353/how-to-add-rendering-extension-to-reporting-services.aspx