If you've already downloaded an old version of mist follow these instructions
to remove it.

1. Clear your %temp% folder
2. Clear the %systemroot%\prefetch folder of its content
3. Delete the MIST folder from where you installed it
4. Delete any shortcuts pointing to MIST and the install files
5. Clear your Recent Document History (can be done from the Task Bar properties,
under Customize/Advanced)
6. Delete all MIST config files on your C:\ root (all the menucommands???.txt fils and all the config???.cfg files)
7. Delete the entry for MIST in the registry under HKEY_CURRENT_USER\Software\Microsoft\Windows\ShellNoRoam\MUICache
8. Empty your recycle bin
9. Download CCleaner (search it in google) and run it with default options.
9. Do a full shutdown and restart your PC to make sure the memory is empty of all
traces.

This should cover clearing up completely any traces of MIST from your PC. This will NOT guarantee you won't get GUID banned if you got caught...