Whilst neither condemning or condoning such a practice you can
first open something else on your desktop, then launch C3. To
change back just use the Alt-tab keys to go to the other application
(Hold down the Alt key and press the Tab key). You should get
a list of open applications when you do this so just keep pressing
the Tab key (while still holding the Alt key) until the required
program is highlighted, then release both keys.
Note this will not be instant as some things may have to be reloaded
(such as the office toolbar), but should only be a few seconds
on a P200 or faster.
C3 should then appear as an item on the start menu, which you
can click to get back into the game.
Since this means you will be wasting several man-days at work,
don't get caught. Also watch how you install the program if others
have access to your machine, either directly or via a LAN. Try
installing to a hidden directory and don't display hidden files