Unable to login Windows Vista as MS .Net Framework installed

Hello,
I need some help regarding .net installation. I installed .net framework but right after installation I failed to login my Windows Vista OS. I have not saved a restore point to restore my operating system.
I have tried to repair it with my DVD but to no avail.
I have tried again to install it, but this message has been displayed.
Thanks for your help.

Error:
An error occurred during setup. Installed files have been removed from your computer. For known issues and troubleshooting information, see the online Readme . For error information, see Error Log.
