That will work in Microsoft Office apps and programs that ship with Windows.
The point is, not all programs will respond Ctrl + b in the same manner, if at all. I assume you are using it in the programs that it normally works in, however. :)
Usually, when keys or key combinations do not work, it is because of a keyboard problem. There are also programs you can use to change shortcuts, like autohotkey. You can also change the shortcuts in MS Office. You can do that by (in your case) right-clicking the Bold button and selecting Customize. On the Commands tab, click Keyboard. In the Category pane, select Format. In the Commands pane, select Bold. If the Current Keys show that Control+B and Control+Shift+B are the shortcuts for Bold, something else is wrong. If they are not, place the cursor in the Press New Shortcut Key box, and press Ctrl+B, then click Assign.