One of two things.
When installing Mapguide Studio, make sure mapguide Server Service is stopped. Next, clean all of your temp files out of c:\docs&Settings\(Username)\Local settings\temp
After those two things this should go thru just fine.
Oddly enough the only way we can install it is by shutting off a bunch of tasks from task manager to the bare minimum. Then it installs fine. Which one is causing the issue I don't know. I never have seena DETE in the task manager so not sure what that is about. This is happening on all of our machines. Map3D, MG and the basics. Even on fresh install machines this seems to be an issue. Very annoying.
The problem was the OS. I used nLite to compile a nice tight up-to-date OS install disk for Windows XP. I disabled system restore completely. I am putting a heavy bet that is what caused this installer issue. Reinstall with original disk no problems. Maybe the installer checks for system restore state and when not exactly normal it bombs like an old Pinto.
When I run this to uninstall DETE it say 'The action is only valid for products that are currently install'.
But when i run
Msiexec.exe /i "E:\mgstudio\DETE\dete" /qf INSTALLDIR="C:\Program Files\Autodesk\MapGuideStudio2008\DETE" /lev c:\mgsydio.log to install DETE it says 'can't find End User License Agreement' ??