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IE6 is an integral part of XP. It cannot be uninstalled. SP2 actually contains the latest version of IE being IE SP2. If IE is damaged the repair procedure is to reinstall SP2.
That being said: a pop-up blocker would not prohibit access to web sites. Only pop-ups within a web site. Are you also running a Firewall (outside of SP2)?
If sites themselves are not being displayed your problem is elsewhere. Do you get the DNS Server Not Found error or what happens?
Anything in common with these sites? Is this a new problem? Did these sites work previously?