This is a common problem for laptops bought in Japan. Japanese laptop = Japanese OS. If you want to convert it to English operating system, you will face a very common problem after converting.
Reason: Windows Vista and Windows 7 somehow identifies some Japanese keyboards as an English device.
Solution: You will need to go to the Registry and tell Windows that you have the standard 106/109 Japanese keyboard instead of the English 101 version.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i8042prt\Parametersand change the following entries to this value:
If you don't know how to do it, here's the step-by-step guide from Microsoft: