Whatever you command as root will be done (as long as there is enough of the system to do it).
Don't do this unless you wish to destroy your installation:
rm -rf /*
Basic system administration
To change to the full root account (system administrator), if you are running X, open an x terminal and use these commands from your user account. Note the change in the prompt. You can do the same from a virtual terminal as well, but you can't open an x terminal to do so.
[fancy@tinwhistle fancy]$ su -
Password: <give root password and press enter>
Remember, now whatever you command in root (it's the "god" mode. You can bless or destroy at your whim) usually gets done if enough system is left to carry out the command.
Sit on your hands and read the commands you type at least 3 times before pressing the enter key when in root.