To uninstall magix, use add and remove programs and then restart.
Next, remove all remnents of magix in user profiles, and program files (including x86)
then you need to remove it from the registry to. Heres something I "Borrowed" from the web and I used it with great success :
Run Registry Editor
Find and delete all registry entries of the program in HKEY_CURRENT_USER\Software\MAGIX AG\, HKEY_LOCAL_MACHINE\SOFTWARE\MAGIX AG\ and HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run\
Find and delete all files of the program in system folders C:\Program Files\MAGIX AG\, C:\Document and Settings\All Users\Application Data\MAGIX AG\ and C:\Documents and Settings\%USER%\Application Data\MAGIX AG\.
NOTE: We recommend only for advanced computer users, manually edit the registry and remove MAGIX Movie Edit Pro because deleting any single registry error leads to a serious problem or even a system crash.