I have read many posts on this and it seems difficult but some have managed to do it. If IE6 came pre-installed then you're stuck with it, but as it is you should be OK since you upgraded.
You could try to run this command and hope it works: w2kexcp.exe /u
Or, in control panel's add/remove programs show hidden.
A suggestion from here :
Open C:\Program files\Internet Explorer.
Right click the folder Uninstall information.
Uncheck the hidden mode and press OK.
Go to C:\Program files\Internet Explorer\Setup.
And lastly, this software can do it for 2000 and XP