So in Windows 8, after you installed your beloved input methods, there will be default input methods that are automatically added, and refusing to be removed.
A word of precaution: if you don't know how to operate Registry Editor, find someone to do it for you to avoid system malfunction. Here's how to remove it.
Press Win+R to open the Run dialog. Type regedit and click OK.
Expand this key: HKEY_CURRENT_USER\Software\Microsoft\CTF\TIP
At this point, you have to expand the Input Method that you want to remove. If you use multiple languages and have a few default input methods, you may have to experiment a bit to find the correct one.
Press Win+Space now, the silly input method is no longer there!