First, go to this site and hit "Support," http://www.symantec.com/index.htm , and get in contact with customer service. As you have a trial version, you should rate free email technical support. I recently had a problem with my subscription to NIS 2005 and though it took some time, the problem is now resolved and my protection was never compromised.
If that doesn't work to your satisfaction, You should decide what anti-virus software you are going to use in the long-haul and go ahead and spring for it now.
I recently purchased the eMachines T6212, which came with Norton Internet Security preloaded for a 90 day trial. Not long after, I started getting the following message in an error window when starting up:
"Norton Anti-Virus does not support the repair feature, please uninstall and reinstall".
If the "uninstall and reinstall" refers to Norton itself, that'll be somewhat difficult, since I don't have the disks.
If anyone can shed some light on this I would be most appreciative.

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