Can't Display Recent Messages in Word 2010

The thread

1. Click the File tab.
2. Under Help, click Options.
3. Click Advanced.
4. Under Display, in the Show this number of Recent Documents list, click the number of files that you want to display.

simply does not work. The "Show this number of Recent Documents list" is grayed out and not clickable.

How do I fix this?

(OS is Windows 7 Home Premium.)

Are you using CCleaner or something similar?
If so, you may need to uncheck Microsoft Office in the applications section.

I am running CCleaner. I have not run it since upgrading from Office 2007 To Office 2010 yesterday. Just now I went to CCleaner/Applications and unchecked both 2007 and 2010.

I'm still unable to show recent documents in Word. Do you think uninstalling and reinstalling Office 2010, with the CCleaner boxes unchecked would fix the problem?

Thank you.