First off, Mundus Magnus has some quite detailed instructions for install, but essentially, you have done the right thing to install it. Check to make sure that when you unzipped the file, that all the files ended up in the right folders. Winzip can be set to ignore folder information, and this would REALLY mess things up

Also make sure you DON'T have ANY other modifications done to your RTW install. Some changes are OK...but it makes it a lot harder to get to the bottom of a problem

As far as backing up goes.....copying and pasting an icon does just that....it does not copy and paste all the files in your RTW folder. There are LOTS of files in the RTW folder, and it shoudl take a few minutes to copy them. I think you just backed up your icon

As far as the install goes....I followed the instructions to the letter and got a fully functioning mod. It does work.