W2K Compatibility with newer NAV products

Because of business software issues I am restricted to running W2K on this machine. I current have NAV 2003 running with old Definitions (01/05/2011). I purchased NAV 2006 and it virtually killed the computer, slowing it to a crawl and causing lock-ups. Had to go back to NAV 2003. The rest of the office computers are all running Win7 and NAV 2012 with no problems. Is there any kind of work around to allow me to either update the virus definitions for NAV 2003 or make NAV 2011+ work on W2K?

 

Any help would be greatly appreciated,

 

Joseph