For Classic UTAU on Windows, please make absolutely sure that your system settings are correct before you download and install UTAU.
This tutorial will go over 4 steps to set up UTAU. Changing system locale Checking the decimal separator Installing UTAU Changing UTAU to English Changing system locale In order for UTAU to work correctly, you will need to set your system...
utaforum.net
You can follow the screenshots in the guide to double check your settings, then download UTAU from here:
http://utau2008.xrea.jp/
The first download link is "v0.4.18e インストーラ" for the most recent version from 2013. The setup tutorial will also explain how to switch the interface to English.
Alternatively, you may be interested in OpenUtau. No special system setup is needed, and it's available for Mac and Linux too. OpenUtau is regularly updated and has many useful features that make it easier to use and more beginner-friendly.
OpenUtau: Open singing synthesis platform / Open source UTAU successor
www.openutau.com