If you are installing RU1 for Exchange 2010 and setup is failing with fallowing error, there is the remedy to resolve the issue.
RU1 install fails with fallowing errors
Setup Wizard for update rollup 1 for exchange server 2010 Service pack ( KB2645995) was interrupted, your system has not been modified. To install this program a later time, run the installation again, to exit the setup, click Finished..
Open command prompt on the problem exchange server with admin privileges
Use copy path on the E210 RU1 by holding Shift key down and paste the shortcut in the CMD window.