Copy file usp10.dll then select on Start button then choose Run...and type: %systemroot%\system32 then click OK

Paste the file usp10.dll into the folder
dllcache

Note: The folder dllcache is hidden by default. so if you do not see it then
Note:
If you can not paste the file
usp10.dll in the folder
dllcache, make sure that you have closed all the applications and then try again. If the same problem still
occur, log out and log in again with a username that has the administrative
privilege. If you still have problem, please try to setup again in
Safe Mode .
If you want to be able to type Khmer Unicode directly in any Microsoft Office applications, follow the following steps:
Copy and paste the file usp10.dll into the folder Program
Files, usually
C:\Program Files\Common Files\Microsoft Shared\OFFICE11
(Office 2003)
C:\Program Files\Common Files\Microsoft Shared\OFFICE10 (Office
XP)

Open Microsoft Office Word ( xp or 2003)
Click Alt + Shift to exchange between Khmer Unicode language and English language
Try typing it. Remember that you have to type as what you spell. You can use the Khmer Unicode Keyboard layout for help. Download KhmerKeyboard.pdf (Layout)