Omg...Norton...omg...Erm...disable it when u DL..or most of the time, only turn on for scheduled scans and activate windows firewall.
norton will make your PC EXTREMLEY slow as it scans EVERYTHING you do, everywebpage, everyfile you open, every program you run.
If u haven't noticed any changes in the speed of your PC, keep it activated. Only disable it for a short period of time.
for example. when u DL a very small file, disable it for 5 minutes ( a selction box should promt you when you try to disable it)