No Virus, Trojan, Spyware Etc.

If posting this in wrong place, please accept apology from this newbie, frustrated, (almost) computer-illiterat, senior woman. Computer extremely slow. Websites taking forever to open. Have used the following to try to locate problem: Avaste Antivirus, CCleaner, HijackThis, Ad-Aware, Malwarebytes, Rootkit Revealer, Win Utilities, and today Spybot. Spybot reported "Congratulations: No immediate threats were found."

Did all the above because someone told me virus, another said rootkit ("Very serious!"), another said something else. Tried them all. According to everything tried, my computer is clean. Could my problems be because I changed from using Internet Explorer to Firefox?

Oh, use Windows 2000 because I still like spiked heels and miniskirts. Old folks sometimes don't like change.

Thank you to anyone who can give me any insight into my problem, or direction what to do next.

At the moment I would suggest you see this post and start a thread in the Malware Removal Forums. A security expert should be able to see what is going with your machine.
http://forums.spybot.info/showthread...932#post394932
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When you say your computer is "slow", can I assume that the websites taking "forever to open" is related to the browser initializing? Not necessarily the internet?

A rootkit is very serious but I would not be sure now until we know what is going on; that is why I strongly suggest you start your thread.