Many AV programs will not continue with the install if they detect another product on your machine.

The best way is to have CD / downloaded file ready, uninstall through Control Panel, then restart machine.

You should then get a warning balloon in the system tray saying you are not protected, that helps to confirm you have removed it ok, you could also run something like www.ccleaner.com to remove any obsolete files.

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Then install ne AV and let it update itself and perform a complete system scan and you should be fine.
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50 cmc with ice = ok for you?