If Items do get into your computer you want to have a back up plan for this I recommend Two programs. AVG is a free antivirus program for those of us who have a tight budget and a pay Program Norton antivirus. These programs scan your computer for virus and remove them from your computer.
I would also recommend getting an ad remover program these type of programs remove spy wear from your computer. Spy wear is a program that takes information from your computer and sends it back to it's master.
Free antivirus: http://www.grisoft.com/us/us_dwnl_free.php
Pay antivirus: http://www.symantec.com/purchase/
Free adawear: http://download.com.com/3000-2094-10045910.html?legacy=cnet ,
http://www.lavasoftusa.com/
Pay adewear: http://www.lavasoftusa.com/
Extra pay adawear: http://www.lavasoftusa.com/
DONT FORGET TO UPDATE YOUR PROGRAMS!