Jesus, Mary, and Joseph! NO! Don't touch applocale with a 10' pole! It's not supported anymore (it was only meant for XP) and actually makes your machine think it isn't localized regardless (I actually tested it when another user said she had issues and I can confirm - it doesn't work).
Your machine will not suddenly become Japanese where you can't read it. Locale simply makes it so that your machine can run programs that are coded in Unicode (like UTAU - it's coded from a Japanese computer). A few programs may change their interface to match the locale language, but it's easy to change those programs back to English.
These steps assume that you're on a machine with a Windows OS that's newer than Vista:
- Open control panel
- Go to Region (if your view is set to icons; otherwise navigate to it from Clock, Language, and Region)
- In Region, go to Administrative tab
- Change system Locale (should be Japan) if you haven't
- Reboot your machine
- Go to control panel again and in Region, click Additional Settings
- Make sure Decimal actually shows a period (shouldn't have to do this with a US machine, but it doesn't hurt to be extra prepared)
- Uninstall UTAU completely.
- Download a new copy of UTAU from the following site:
http://utau2008.xrea.jp/utau0418e-inst.zip - don't keep or reuse the copy you originally downloaded. It's probably corrupted and will render mojibake.
- Attempt to install the new copy of UTAU
- When it's done installing, test Defoko/デフォルト (called uta in the voice folder) by making a note. If you get the hiragana for 'a' (あ) and can play it back without issue (using the default resampler.exe, NOT having resampler.dll checked), then you're good to go and can proceed learning how to work with your own bank.