Hello there, and Welcome
Please let us know what version of the Symantec product you have. Although I assume an anti-virus.
If you are going to install another AV, it would be best to go about completely removing Norton. Although it would not be a good idea at all to use any third-party uninstallers the may be available, at least not before using the one(s) supplied by Symantec which could be from their website or your computer. You should first look on Add/Remove Programs and the Start Menu to see what uninstallers are already available.
See this Google search and try appending the version details, such as its year...
http://www.google.co.uk/search?num=1...tall+antivirus
Regards,
M_M