You don't need to uninstall v6 to install v7 - it just upgrades the old version. If it's telling you to uninstall, something has gone wrong. If you use the Windows Update site, it will do it for you.
IE6 is installed/removed as a Windows component, not a program.
To uninstall 6, you press START - CONTROL PANEL - ADD/REMOVE PROGRAMS (Yes, really). But it's not in the 'Programs' area. Click on ADD/REMOVE WINDOWS COMPONENTS. In there you will see IE 6 and it's perfectly OK to remove it.
If you don't see it:
-Open C:\Program files\Internet Explorer.
-Right click the folder Uninstall information.
-Click Properties
U-ncheck the "hidden" mode and press OK.
-Go to C:\Program files\Internet Explorer\Setup.
-Run setup.exe
But - I'd recommend going to Windows Update. Something is wrong if it's telling you to uninstall version 6
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