iTunes is not opening after update in Windows 7

I recently updated my iTunes to 11.1.5.5 and it is not opening and when i click it says "The folder "iTunes" is on locked disk or you do not have permissions for this folder."😠😠

I've tried running it as "Administrator" but nothing happened. Then i reinstalled it and again nothing happened and thirdly i read an article on apple support "http://support.apple.com/kb/ts2363" and followed every step but nothing happened it keep on displaying "The folder "iTunes" is on locked disk or you do not have permissions for this folder."

now what to do.... ?

please help as soon as possible because i've to sync my iPad and iPhone.

Seriously hate this thing......