Can I run multiple IDE instances simultaneously?
Yes. You just need to make sure that you run each instance with a different userdir: FaqAlternateUserdir.
If you try to run a second NetBeans instance with the same userdir the first one will simply receive focus; it is not possible to run two instances with the same userdir.
Applies to: NetBeans 3.6, 4.x, 5.x, 6.x, 7.x