I can't uninstall my iTunes, it always say specified account has already exists !! help?

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.

See Note 1 below the second box. I think you may need to use the Program Install & Uninstall Fixit to get past the "specified account already exists" warning.

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 theiTunes 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.

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

tt2