Reverse these instructions I imagine
http://support.microsoft.com/kb/280725
To resolve this problem, change the layout to Japanese 106/109 keyboard:
Click Start, point to Settings, click Control Panel, and then double-click System.
On the Hardware tab, click Device Manager.
Click the plus sign (+) next to Keyboard to expand the branch.
Double-click English 101/102 Keyboard or Microsoft Natural PS/2 Keyboard.
On the Driver tab, click Update Driver.
Click Next.
Click Display a list of the known drivers for the device so that I can choose a specific driver, and then click Next.
Click Show all hardware of this device class, click Japanese PS/2 Keyboard (106/109 Key), and then click Next.
Follow the...