|"I uninstalled a trial version of norton and, unfortunately, the problem persists."|
By any chance were you trying to install a full version of the same software??
My brother had a hexx of a time when he tried to un-install Norton Antivirus 2005 or 2006 and then install it again on a different hard drive. In his case the second time he ran it (and therafter) the installation would blank out a message window after a certain point and he could go no further. I went to his place and tried to figure out was going on but got nowhere. He found out later he wasn't seeing an error message he was supposed to see (bugs in the program) that would have let him know what's going on. He tried some suggestions on the Symantec site and got farther, but still no go.
He only found out what was going on later.
The real problem turned out to be the software has anti-piracy protection - as I recall Symantec started doing that in 2004. Information about the installation is sent in the background while you're installing the software without that being obvious (although, there may have been info about that in the license agreement you have to agree to, but who bothers to read all of those ponderous things) to a Symantec web site and kept in some database. Apparently once the software has been successfuly installed once, NO ONE, not even the legitimate buyer, can install the same software again - when you attempt to, the datbase info is consulted during the installtion, and the install fails, if the info about that software being installed already is there. He emailed Symantec but it took them ten days or more to reply - they told him they had removed the info stored on their web site about the software installation so he could install it again, but by then he had already gotten rid of it (threw it away), and he says he'll never install Symantec software again unless they fix that problem, or at least build something into the installtion software so you know what you need to do, and make it possible for Symantec to delete the info in a very short time. There was nothing obvious on the Symantec web site at the time that would have led him to info about what the problem was.
If Symantec is still using the piracy protection, which is very likely, that may be what's going actually on in your case too.
Our family used to use Norton products for many years. Several versions of Norton Utilities, of Norton Antivirus, and of System Works ( = Norton Utilities plus anti-virus) - I have System Works 2001 and still use it but I can't update it's anti-virus anymore. It's too bad their software has gotten to be bloatware and it it has a reputation of slowing down your system more than most anti-malware software does (at least, in 2006 it did).
On the other hand, Symantec probably has more people working on solving malware problems than any other company in the world. However, no one anti-malware software detects and gets rid of everything anymore in any case.
As a side note.....
I found out thru experience that if you have installed certain Norton anti-malware products before installing XP SP3 updates, the SP3 updates installation will fail to install, even if you disable everything you can in the Norton software's settings. You have to un-install the Norton software first, then the SP3 updates will probably install successfully, but if the Symantec anti-piracy situation is still the same, you have to contact Symantec and get them to delete the installation info from their web site before you can re-install the Norton software.
In other cases, the SP3 updates install, but a whole bunch of things are then not working right in Windows - Symantec and Microsoft has the fix for that problem.
Often all you need to do with most anti-malware software before installing SP3 updates is to disable the components of it that are running all the time Windows is running, looking for suspicious activity. It's a good idea to do that whenever you install major software.
With AVG 8.x, all you have to do is disable it's Resident Shield in it's settings before installing the SP3 updates.
There are other anti-malware programs that cause problems if they have been installed before installing SP3 updates, but as far as I know none have the same anti-piracy situation as Symantec.
You don't need to buy anti-malware software.
If you do buy it you'd probably be better off buying another brand, if the Symantec software still slows down your system more than most .
Free anti-malware software is often included with the ISPs services you pay for - check out their web site! You merely have to download it.
Good free versions of anti-malware software - AVG 8.x, Avast!, Malwarebytes, AdAware, etc. etc. (I don't recommend Spybot).
Good paid versions? The paid versions of the above mentioned, or check out Tuccows or other major software download sites and heed the User ratings of both the paid and free versions.