Specifies the order in which Windows Installer searches for installation files.
By default, the Windows Installer searches the network first, then removable media (floppy drive, CD-ROM, or DVD), and finally, the Internet (URL).
To change the search order, enable the setting, and then type the letters representing each file source in the order that you want Windows Installer to search.:
-- "n" represents the network;
-- "m" represents media;
-- "u" represents URL, or the Internet.
To exclude a file source, omit or delete the letter representing that source type.
n = network, m = media (CD), u = URL
A few valid examples: nmu, n, nu, mn