Hi Steve
The security updates will be from windows. The updates are there to fix security vunerabilities in the windows xp operating system. If you remove them it could cause problems with windows so i would recomend you just ignore them. If you are having a few issues with your computer its allways recomended to do a spyware/malware scan and defrag the hard drive. A good anti malware program that i use a lot is malwarebytes and you can get it free from www.malwarebytes.org.
Regards
Mark