Windows verification software

I am one of those people who do not have a registered Windows license for my HP Pavilion Notebook. When it was taken in a couple of years ago for service and an upgrade, they just loaded one of their own versions. What options does that leave me with? I am set to receive Windows Automatic Express updates, but can't get Windows Defender or the latest browser update for Internet Explorer. My computer was later upgraded from Windows XP Home Edition to Windows XP office edition.
My Windows Defender worked up until the end of December 2006. I since removed it from my computer so what options do I have now. I use Symantec
Virus updates on a daily basis. Do I really need Windows Defender? :wave

 

One, either buy a new copy of XP.
Two, if you have the paper work, have the company who upgraded/fixed your computer, put it back to what it was.
Three, report the company to MS for installing illegal/pirated OS on your computer.

 

What is Win XP office edition?

 

As far as I know, win office xp edition is MS office 2002.