ITUNES problem

Hi there, firdeboer_85!
Thanks for reaching out to the Apple Support Communities! It sounds like you have been having issues using iTunes and I am happy to help out! Based on what you are describing and the steps you have tried, I would recommend taking a look at this article If you can't install or update iTunes for Windows. This will give you steps to try along with links to other great articles you can take a look at that are recommended by Apple in this situation you are having including the Apple steps to uninstall iTunes.
Let me know the results and have a great day!

Typically that error is caused by a sticky copy of Apple Software Update that won't remove itself when requested. Try repairing that first. Then try installing iTunes again.

For general advice see Troubleshooting issues with iTunes for Windows updates.

The steps in the second box are a guide to removing everything related to iTunes and then rebuilding it which is often a good starting point unless the symptoms indicate a more specific approach. Right-click on the setup file and run the installer as administrator. In some cases you may also need to disable any non-Microsoft anti-virus software while installing.

Review the other boxes and the list of support documents further down the page in case one of them applies.

The further information area has direct links to the current and recent builds in case you have problems downloading, or want to revert to an older version if the current one won't work properly for you at the moment.

Your library and device backups should be unaffected by these steps but there are links to backup and recovery advice should it be needed.

tt2