Uh, actually that's extremely unlikely in my case but I'm not going to argue. I just offered my personal experience. YMMV.
Not unless you reinstall your OS from known, clean media on a regular basis.
Malware scanners and anti-virus software only help you after you get infected and only if the software can detect the malware. Malware writers have become exceedingly good at evading detection.
Report: 48% of 22 million scanned computers infected with malware
That's half. One out of two. So here's the experiment:
Ask the person next to you if they are infected with malware. If they say no, then it's you.