What is Risk Tracer?
http://www.symantec.com/business/support/index?page=content&id=TECH102539&actp=search&viewlocale=en_US&searchid=1341943696488
About Risk Tracer
http://www.symantec.com/business/support/index?page=content&id=HOWTO27137&actp=search&viewlocale=en_US&searchid=1341943696488
Because it polls every second, it *may* affect PC performance. Personally, all our machines have good specs and we've run risk tracer ever since SAV. Have never seen any issues. I wouldn't ever consider turning off risk tracer. Has helped out a bunch, especially with Conficker.
Also note: Risk Tracer relies upon the Windows File and Printer Sharing. If this is disabled (as per MS Article 199346, http://support.microsoft.com/kb/199346) Risk Tracer will not work.