ynwia,
Turn the monitor on without plugging it into the computer. Do you see anything? Most, if not all, monitors have some type of information box that is displayed telling the user to check the signal cable. Does anything like this appear? If so, the problem is either your cable or video card. Otherwise your monitor is busted and probably not worth fixing, especially if it's > 5 yrs. Ave. life of the tube is ~8-10 yrs.
J_