Q: error 7 (windows error 127)

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. (Yes, I see you have done this but perhaps not the specific deletions that are mentioned.)

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 QuickTime or third party software.

See also the section Install missing components in case installing one component at a time is successful.

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