Uninstall PostgreSQL & try the following steps:

1) Run cmd.exe as Admin (Start > Search 'cmd' > Right-Click > Run As Admin)
2) in CMD window run (type the code then hit Enter key) following command:
net user postgres /del
3) Reboot PC
4) after reboot open cmd.exe again & run following commands:
net user postgres postgrespass /add
net localgroup Administrators postgres /add
net localgroup Users postgres /delete
runas /userostgres cmd.exe

When it asks about password please input postgrespass & don`t worry if you don`t see any new symbols\inputs in cmd window. If you did all steps right then you should get new cmd window for postgres user.

5) Download PostgreSQL installer (http://get.enterprisedb.com/postgres...-1-windows.exe) & move (copy/paste) it from the \Downloads folder to C:\
6) in new cmd window for postgres user run following commands:
cd c:\
start postgresql-8.4.22-1-windows.exe