Problem With Windows calander

Thanks for reading.

I am tring to use Windows Calander, however, when I try to insert an appointment I get a message that it is disabled. I When i hit details it says access denied. I tried to research it last night on the windows help and thought I had followed the exact directions but it is still not working.

I had used it about a month ago and it worked fine. For the last month, I have been using the calender on my word processer which I believe is "Works ".

Any thoughts will be appreciated.
Thanks
Thomas