Right click on your task bar and click on task manager, click on that and you'll see a tab called applications... look to see if the program is still running. if it is, End Task.. if not, go to the Processes tab and find Microsoft Works.exe file and End Task on that.
Make sure that you have looked to make sure that there isn't anymore hidden in the Processes.
Then close Task Manager and try to reopen the file you're wanting.