I downloaded and installed today the Netbeans 6.7 and for my surprise its IDE was in Portuguese. I prefer using the IDE in English, so I tried to change it using the way I remembered from previous versions, i.e. at the Tools menu. As it happens, it is not possible to change the language of the IDE through the interface, because it is based on the locale of your machine.

After some experimenting and searching I found out that it is necessary to pass the locale to the IDE and force it to use something different from your system. So, go to the shortcut which starts your IDE (yep, using Windows here) and pass "--locale en:US" in the command line.

It should look like this, depending on your Netbeans installation directory:

"C:\Program Files\NetBeans 6.5\bin\netbeans.exe" --locale en:US


Another solution (and this SO agnostic) is to open the "netbeans.conf" file which is at your Netbeans installation directory "etc" folder, e.g:

C:\Program Files\NetBeans 6.0.1\etc\netbeans.conf


Find the Netbeans default option line which should look like this:

netbeans_default_options="-J-client -J-Xss2m -J-Xms32m -J-XX:PermSize=32m -J-XX:MaxPermSize=200m -J-Xverify:none -J-Dapple.laf.useScreenMenuBar=true"


Now add "-J-Duser.language=en -J-Duser.region=US" to the end of this line, turning it into:


netbeans_default_options="-J-client -J-Xss2m -J-Xms32m -J-XX:PermSize=32m -J-XX:MaxPermSize=200m -J-Xverify:none -J-Dapple.laf.useScreenMenuBar=true -J-Duser.language=en -J-Duser.region=US"


By the way, this should work to all the most recent Netbeans versions.
Cheers!