Q: can't reinstall iTunes

The general troubleshooting advice when iTunes fails to install properly (and reinstalling or repairing it does not work) is to remove not only iTunes but ALL related components, reboot, remove the target installation folders and reinstall.  See turingtest2's excellent iTunes for Windows Troubleshooting Guide at:

Troubleshooting issues with iTunes for Windows updates

especially the section:

Removing and reinstalling iTunes and other software components

for details on how to do this.  There are also many other helpful tips as well.

Typically that message indicates an issue with the current version of Apple Software Update. Repair Apple Software Update from the programs & features control panel, and then try 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.

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, need to revert to an older version or want to try the iTunes for Windows (64-bit - for older video cards) release as a workaround for installation or performance issues, or compatibility with third party software.

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