no problem, the very safest way would be to run in a sandbox, that way nothing would get to the harddrive at all.
sandboxie used to be free , but I believe that you have to pay now.
360 Internet security by Qihu has a sandbox.
you might google for others.
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Knock on wood but I have been safe so far,
I run 360 Internet security by Qihu as real time antivirus
Malwarebytes as an on demand scanner, at least once a week
Spywareblaster
Malwarebytes AntiExploit
Windows Firewall
Web of Trust
Adblock Edge
Adfender
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I run ccleaner everyday, not the registry!!
defrag once a week
run checkdisk after every power outage, or at least once every couple of months.
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that is my setup, read around and see what others are running, it really depends on what you do with your pc. I use mine for mostly surfing the forums, watching youtube, searching google and playing solitare. The other user on this pc does yahoo mail, and facebook, besides surfing.