Are you saying you want Japanese support in programs that need it, but English as the default and no IME? To my knowledge you can't get Japanese menus in Windows Explorer and other Windows apps without the IME. But I did find a combination that gives me Japanese when I need it, and English everytime else, although sometimes 3rd party apps (namely those by Adobe and Apple) don't play by the Windows design rules and still come up as Japanese on me. Don't know if the same setup works as well in Vista though.
All of this happens on the Regional and Language Options control panel app:
1 - Ensure East Asian files installed on the Language tab.
2 - On Advanced tab, check the Japanese codepages 20932, 50220, 50221, 50222, and 932.
3 - On Advanced tab, set language for non-Unicode programs to Japanese. (This makes most older games use Japanese)
4 - On Regional options tab, set your Standards and Location to whatever you like (such as English and United States) (this makes Explorer and "good" Windows apps use English)
5 - Click that Details button on the Languages tab, the remainder of the steps all happens there:
6 - Set default input language to English and keyboard service to US (assuming thats what you chose in step 4) (this makes it so when you type you don't get kana)
7 - Click Language Bar button and uncheck the "Show on desktop checkbox" (This hides the IME controls)
8 - On the Advanced tab of Text Services and Input Languages window, uncheck the two checkboxes there (This makes it so non-Unicode but CodePage aware apps like Notepad don't try to bring up the IME on you.)