This can be the effect of a policy having been applied or perhaps a corrupt registry key. Check this by going to Start, Run, typing MMC and clicking OK.
When the program opens go to File, 'Add/Remove Snap-in...' and click the Add button. Highlight 'Group Policies' in the list then click Add, Finish, Close, OK. Click the + to the left of 'Local Computer Policy' to expand the branch. Next expand 'User Configuration', 'Administrative Templates', 'Windows Components', 'Internet Explorer'. Highlight 'Internet Control Panel' and you should see a few options appear in the right-pane. Double-click 'Disable Content page' and you will see 3 radio buttons labelled 'Not Configured', 'Enabled' and 'Disabled'.
If 'Enabled' is checked then check either one of the others instead. On a system without any policies set it is normally 'Not Configured' that is set. If 'Enabled' isn't checked then I sometimes find that it helps to first check it and click Apply before checking 'Disabled' and Apply again. This can sometimes reset a corrupt Registry key.