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isnt multiple virus "Viri" or something 
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That's right 
I make backups... wait a minute, what did I say? 
B A C K U P . 
That's right, guys and gals, I said the magical word 'backup'. I've safely put all important documents:
- on a second HD,
- on a ZIP disk,
- on a second PC.
The only way I can lose all my data is if this room goes up in flames, so the only thing I've to do in case of an emergency (virus which can't be removed by my virus-scanner) is format the HD, reinstall the OS and get my files back from the backups I've made.
Oh, and I don't open weird emails (attachments), files from unknown sources, I don't run programs which can be possibly dangerous, etc.