If you try to install and open the NetBeans IDE in a Japanese environment, you'll get your menus and messages in Japanese. This is true even if you chose English in the Netbeans download page. The reason for this is that Netbeans is multilingual and will start with the locale of your system -- which is usually set to Japanese Locale for people like me who use Japanese Windows OS.
Of course, you can change your system locale to English but it isn't ideal as it may affect other programs that depend on the system locale settings. What I suggest is that you set the "--locale" start-up option to English when you run Netbeans.
For example, you can open a command prompt window, change to the bin folder that is under your netbeans installation folder (e.g. C:\Program Files\NetBeans 6.5.1\bin) and start the Netbeans IDE by typing the ff:
netbeans --locale en
Alternatively, you can specify this start-up option in the netbeans.conf file that is located in the etc folder under your NetBeans installation folder (e.g. C:\Program Files\NetBeans 6.5.1\etc\netbeans.conf). To do this, open the file in a text editor and change the value for the option "netbeans_default_options" by inserting "--locale en".
For example, this is what the line looks like before I inserted the option:
netbeans_default_options="-J-client -J-Xverify:none -J-Xss2m ...
This is the line after I changed it:
netbeans_default_options="--locale en -J-client -J-Xverify:none -J-Xss2m ...
Once you've modified netbeans.conf, you can start Netbeans as you would normally do and you will get all UI elements in English.