will spywareblaster work correctly even if i do not upgrade my xp pro sp2?

I bought my computer at a flee market, and i think that the windows xp pro sp2 is a bootleg copy. every thing is working good and i don't want to mess anything up or get in trouble or lose my xp service so i am not upgrading it. I am also not upgrading or updating my internet explorer and my microsoft vertual machine. all of these programs work great as they are. My question is .. will spywareblaster run ok if i do not upgrade or update them 3 programes? I will still update my norton antivirus and any spyware programes i download. Also does spywareblaster work good with norton antivirus? I don't have any spyware or adware removers installed yet and am waiting on a responce from yall b4 i do load them . if not updateing xp an ie will b a problem what can i do to protect against these problems with out having to upgrade?

thx freckelscc