Hello nicolini,
It sounds like iTunes quits unexpectedly everytime you try to open it so you can no longer use it. I recommend the troubleshooting steps in the following article to help you troubleshoot the issue here, named:
iTunes for Windows Vista, Windows 7, or Windows 8: Fix unexpected quits or launch issues
Start with these steps to open iTunes in Safe Mode to see if a 3rd party app may be interfering with iTunes. There is additional troubleshooting to be done in the article if this is not the case:
Open iTunes in Safe Mode to isolate any interference from plug-ins or scripts not manufactured by Apple.
- Hold down Shift–Control while opening iTunes. You should see a dialog that says "iTunes is running in safe mode" before iTunes finishes starting up.
- Click Continue.
- See if the issue you're experiencing persists in Safe Mode.
If you have the same issue while iTunes is in Safe Mode, proceed to the "Create a new user account" section. If you don't experience the same issue, follow these steps to remove third-party plug-ins.
Thank you for using Apple Support Communities.
All the very best,
Sterling