What’s the best PC security/Firewall out there??

I've recently had a desktop hijacker (I think that's what it was… It changed my desktop background and screwed up my security settings)….But right now it seems to be running O.K. However there are a few little thing that it will not do like before.

1) Every time I try to run a Norton scan..It will not let me. Error messages…Server busy…Etc….I tried to delete and reinstall…But It will not allow that either. It seems to block any program that tries to install or remove something.

2) I was going to install Windows Live OneCare..Is this a good program?? It goes half way and also fails to download?? (As soon as I can get my computer to install something, I'll feel better…I'm afraid to enter any passwords right now…)

Is there a box to uncheck somewhere that will allow me to download these programs??? Do I need a new server?? Thank you for the help!!

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