Running more than one antivirus program on a computer can cause system instability, as the two applications will conflict. If Norton antivirus software was installed on your system at any point in time, complete the following steps before installing your ESET product:
To download, save and run the Norton Removal tool for versions 2003 to 2010, click here.
After Norton (or any other antivirus software) has been uninstalled, download an ESET security product. Click Home Downloads or Business Downloads, depending on your license, and then click the Download box to the right of your desired version.
Click Start→ All Programs→ Norton Internet Security→ Uninstall.
Follow the on-screen instructions to uninstall Norton Internet Security.