Disabling IME input in Windows
From Vim Tips Wiki
created January 4, 2004 · complexity basic · author Avery M. · version 5.7
Often, your Windows locale will reflect a foreign country (e.g. Japan) so you can write text in another character set, but you don't want Vim to do that by default. It is annoying to have to disable IME input every time you start up Vim. But it's much easier than that. Simply add this line to your vimrc:
Now, you will start out in regular Roman input mode, without IME.
imcmdline and imsearch can also be disabled in the same way.