A new security feature in Windows Vista is Data Execution
Prevention (DEP). DEP will monitor Windows
services and programs and protect harmful code from executing or
running in system memory locations reserved for Windows and other
programs. Once DEP realizes an attack is in progress, it will shut
the program or service automatically and notify
you.
By default, DEP will only protect Windows and not other
programs. You will have greater security protection by enabling DEP
on all programs and services. If you
have a program or service that doesn’t play nicely with DEP, you
can turn DEP off for that particular service.
Follow these steps to turn DEP on for all Windows programs and
services.

Your should be able to install your nx5 software now.