If "normal c++" means using just the standard library, you can remove files: http://www.cplusplus.com/reference/clibrary/cstdio/remove/ but not changing the desktop background as that is specific of the Operating System, so you should use external libraries.
Unless you want to use non-standard you can't do things like that.
It's a bad habit to get into, but you can use system() commands. The syntax is just system("command"); and you can use any command you can through command prompt, for example system("SHUTDOWN -param -param -param"); where -param are the parameters (like -s). That is, if you're on Windows. On *nixes it's a little different thought.