A 1069 or 7000 login failure error when starting the VPOP3DB service usually means that something is 'wrong' with the vpop3postgres account in Windows - the password may have expired, or someone may have reset the password.
You need to check the account, set the password to never expires, and if that doesn't work, reset the password both in the account, and in the Windows Services list.
If VPOP3 is running on a Windows AD Controller, then go to Start → Administrative Tools → Active Directory Users and Computers. In the Users list, find vpop3postgres, right click, and choose Properties. Check all the settings, including:
Go to start → Control Panel → Administrative Tools → Computer Management. On the left, find System Tools → Local Users and Groups → Local Users. In the Users list, find vpop3postgres, right-click, and choose Properties. Check all the settings, including: