NISS 2009-Want to add add'l browser - need recommendation

have intel pentium4 processor 519K

 

NISS 2009 ver. 16.8.0.41) /I.E.8/SP3 

 

hello -  heard today on T.V. Clark Howard - best to have more than just one browser for 'many reasons' (one being if the other 'crashes)   ... do you all prefer Firefox /opera/ google chrome - (he leaned towards Firefox or Google Chrome)...

Which is the latest version of each ? How do i find the website that is legitimate for the download?

 

when  i download and then install,  do i disable my NISS 2009 'and' its firewall? 

 

  do i upgrade to NISS 2010 before or after the installation of the ''additional' browser' ?

 

  when  i stop using IE8 can i leave it installed but just not 'launched' when using whichever new browser i install ?  they won't 'fight?!    any other 'hints' would be very appreciated.      

            thanks in advance - Edythe