The “Meiryo Bold” font may be used on some Microsoft Input Method Editors (IME) User Interface components where the “Meiryo Regular” font is expected
Consider the following scenario. You have a computer that is running Windows Vista or Windows Server 2008. After you install the update that is described in Microsoft Knowledge Base (KB) article 975929, the Meiryo Bold font or the Meiryo UI Bold font may be used for the Microsoft Input Method Editors (IME) Candidate List or for the Microsoft IME pad Character List. These lists are where the regular weight of the corresponding font family is expected. Additionally, this issue still occurs if you uninstall the update KB975929.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB981584.