If you are logged into your computer as a user with restrictions, or an admin user other than "Administrator", you can set Mixcraft to "Always run as administrator" to work around some of the security issues introduced with Windows Vista and Windows 7.
- Right click the Mixcraft shortcut on your desktop or within your start>all programs menu
- Choose "properties" from the resulting menu
- From the "Shortcut" tab, click the advanced button
- Check the box marked "Run as administrator"
- Click ok
Using that shortcut, Mixcraft will always run with administrator rights.