Windows 7,vista and xp operating systems are used by everyone and can get infected just by going online.most infections comes through your internet connection,even if it's wireless.The hacker comes through your IP address which you get through your internet service provider(ISP).Even if you have a firewall and virus protection,the hacker can still get through to your computer.if you have a popup blocker they can come under your blocker.
I would use AVG "FREE" anti-virus and AVG security,
Never use any "FREE" scan to check for spyware or viruses,for they will load their spyware or virus on your computer,they give the "FREE" scan so you will have to buy their software to get rid of their spayware or virus.
If your computer is slow, it's can be due to using limewire or frostwire or porn or any website where you can get "FREE" music or movies.Your computer slows down because the music industry and the movie industry will load a tracking cookie to track what music and movies you are downloading illegally.
Spyware and Virus removal software can remove and get rid of tracking software,key-logging programs which keeps track of the keys you type and malware which can track your credit/debit card and check info amd your pin number and any online banking you may use.
Iwould like to share with you a "NEW" software called spyware cease!