Spyware Problems

I am currently having problems with the speed of my browser (Internet Explorer) and I think it's related to spyware.    I recently made the mistake of clicking on something that installed "Power Scan 1.1" on to my system which is run by XP Professional.   I subsequently upgraded to Norton Antivirus 2004 Professional and uninstalled the programs that appeared to be causing the interference.  Incidently, my scans before and after the upgrade never identified a "virus" but the impact to the almost constant pop-ups has been obvious nonetheless.  Also, I don't seem to be having any problems/delays at all with my outlook mail.

Again, my problem seems to be mainly related to my browser.  When navigating on sites it is typically taking 2-3 seconds for my prompt to catch up with my keystrokes and there are also delays in pulling up sites and pages as well.   I'm wondering whether I need to purchase more spyware software or just call an I.T. doctor.  Hope someone can help.