Will not FULLY shut down

Hoping someone can help.

I am a senior and not computer technical. A friend has given me his Dell
superseded desktop computer running XP Professional and I am grateful for
his gift.

Unfortunately, it has a problem insofar It will not FULLY shut down after I
pressed the Turn Of button. The computer goes thru the normal states, like
"Saving your Settings" etc. until only the empty blue windswept motive
screen is left and keyboard and mouse are inactive. But the computer itself
is still running. I can only close the computer down by pushing and holding
the On-Off button. This cant be good for the system and I am afraid that I
damage the windows system.

I can't afford the $100.00+ fee a technician would charge to fix it and hope
that someone on this news group can walk me through the steps to overcome
this problem.

Thanks, John