So your 'piece of string question' you ask to install 'any software' but then do a 'such as Excel viewer'.
EVERY APP IS DIFFERENT
You have made it this site, so, read up on each app you have to do, and also, just try installing it and have a play with the app. Look at vendor support sites, there is plenty of information on the Microsoft site for deploying office using the XML files. They generally fit across the family of apps. Most of them have pretty good info on doing silent installs, some don't, that's what makes it 'fun'.
Sign up today to participate,
stay informed, earn points and establish a reputation for yourself!