NIS 2010 with NAV2010?

I have NAV2010, but not NIS2010.  Am thinking of installing the firewall in NIS2010 or the WinXP firewall.  I used NIS a few years ago and had problems with system resources when it was on.  How is it now in comparison to WinXP firewall?  Currently, I am not running a firewall.

 

What are the pros/cons of NIS2010.  I'm running a Dell Dim 8300 with 4m of memory and WinXP SP3 and NAV2010.  I have SpySweeper, Spybot, and Malwarebytes installed, but run them periodically in manual mode for scans, but do not have them running in live mode.

 

Thanks for any insights.

gumboman