When trying to install the Atmel studio you might sometime see this error, i.e - "Windows Installer service is unavailable. Another Aplication May Be Running Setup.". This can be due to many reasons out of which i will lay down some that i am aware of .
1. As the message says please see if some other installation is running. If you can't figure out then from Task Manager kill all "msiexec.exe" process. Make sure you are not running other installations.
2. The windows update service might be installing updates in the background and hence you might be blocked with a parallel installation.
3. Some installer had ran installation and required restart, but we have started our installation by the time.
So for case 2 & 3 , please restart your machine and try installing again. Don't give up, Atmel studio ain't gonna knock you down :)