Another reason to update your software is that more threats will have been detected since your last probable update and so your chances of catching and eradicating spyware will be greater.
One note though, Defender is only compatible on windows xp service pack 2 and greater I believe.
What is your pc running now?
To find out you can right click on "my computer" and click properties.
The window that pops up should should you what your operating system is and what service pack level you are at.
Here is the link to Windows Defender download site:
http://www.microsoft.com/downloads/...-AFA4-F7F14E605A0D&displaylang=en&mg_id=10134
I'm not too sure how to shorten that up sorry.
Please note. It is advised on this site to use more than one anti spyware / malware program as each has its strengths.
My list of programs that I use is:
Windows defender, Spybot Search and Destroy, Lavasoft Adaware SE personal, AVG Antispyware, Super AntiSpyware,
I also run Avast! antivirus software on top of that as well as a firewall from Sunbelt (kerio)
Also check this forun thread for more helpful hints:
http://forums.techguy.org/general-security/603629-security-help-tools.html
Hope this helps you,good luck.
DF