Program installation without reboot
 

My installer cannot rewrite DLL which is used by other processes and write-protected. I need to avoid reboot after installation. Is there any tool in NSIS installer to alert user if a file cannot be rewritten and show list of programs which need to be closed before continue installation?

This may work, totally just a guess though.

http://www.sysinternals.com/Utilities/Handle.html

You may be able to call this program, and have it dump the results to a text file, and then parse it with nullsoft, to fine what your looking for.