How to preserve NIS license when upgrading from Vista to Win XP?

Hi,

 

I was just wondering how do you deregister a license? Is it good enough to run the uninstaller?

 

Also I got a complimentary license to NIS though I don't want to use it right now until my others expire. Are there time limits for which or when you must activate the key?

 

Thanks.

 

Dave.