Do not delete Files in "C:\Windows\installer" On SharePoint Servers

Never delete the Install cache folder %windir%\installer to free up some disk space. This will cause serious problems during service pack upgrades! 

In one of my case, It happened. Installer folder was deleted and when I tried installing the Service pack 2 , It scolded me with this error:

"The detection failed, this can be due to a corrupted installation database."

Workaround is: I copied the files inside Installer cache from other SharePoint server and ran the upgrade again. It worked!

Read more: http://www.sharepointdiary.com/2012/01/do-not-delete-files-in-cwindowsinstall.html#ixzz3UckfrVGN