Norton is not recomended for slower machine or insuffciency of RAM. Usually a inupgraded laptop should have 256 MB. Norton will make it slower because Norton has multiple protections and take a lot of memory once you start your machine.
Actually McAfee is under the same company with Norton,both from Symantec too. I don't recomend McAfee because it can't detect some spywares...Curently I'm using Norton and it performances well and excellent. It almost block every malicious...

__________________
~^.^~Do our best~^.^~