go to the Control Panel => User Accounts => create a new
user, be sure the newly created user has LIMITED account type,
this is very important, otherwise postgres will fail again. Than
you just use this user account in postgres installer.

The reason for this problem is generally caused when you trying
to install postgress on Domain Controller or other machine with
Active Directory.
Regarding the second installation:
The uninstall process does not delete the cretaed user (postgress
by default) and his profile directory (not the database folder).
Before installing postgress make shure that the user is not exist
anymore and that the datafolder is empty.