Very important!!!.....my computer is at stake!!!!!!!!?

i really need help on reinstalling my norton antivirus, believe me its not as easy as it sounds.okay i dont know what happened but my computer was on standby and when i turned it on again there was a security alert on the screen of my computer that said "virus protection is turned off,open your norton product to resolve these issues,and i opened my norton antivirus and kept on checking autoprotect in the little box next to it in the options button,and everytime i hit submit and went back to check it,the box was still unchecked so i decided to uninstall and reinstall my product i uninstallled it but reinstallation didnt really work,when i try to install it again is says that the MSI must be opened throughout the process and when it starts to instal it halfway in the process an error message pops up and says that a certain file couldnt be opened and then another window pops up and says that instalation failed and the process must be terminated or closed,what should i do! whats MSI? HELP!

Very important!!!.....my computer is at stake!!!!!!!!?hijackthis

MSI stands for MicroSoft Installer. Similar to an exe. You should first do a FULL scan of your drive (update your definitions first with live update). If theres nothing found, uninstall it, reboot and reinstall it. What version u have??? Maybe theres a program screwing with the settings. New version os NAV prevent that. Contact me if u need help