What version are you reinstalling? Are you reinstalling your DB (is the old \data folder there)? Or did you delete it all and reinstalling fresh DB?
1) Uninstall PostgreSQL from the Windows Control Panel.
2) run the command - start > programs > accessories > command prompt > right-click > run as administrator
[PHP]net user postgres /delete [/PHP]
4) reboot.
Install postgresql. If you do want to use your old \data folder make sure you do not Initialize Database Cluster.
