Problem with installing PostgreSQL

I am getting the error message when installing PostgreSQL as follows:
"Problem running post-install setup. Installation may not complete correctly
The database cluster initiation failed"
I am using Vista but have changed all User Access settings etc and am running the program as an administrator.
Have uninstalled and reinstalled postgreSQL completely as shown in the guides, but am still having the same problem.
Would greatly appreciate any advice on how to fix this problem.
"Problem running post-install setup. Installation may not complete correctly
The database cluster initiation failed"
I am using Vista but have changed all User Access settings etc and am running the program as an administrator.
Have uninstalled and reinstalled postgreSQL completely as shown in the guides, but am still having the same problem.
Would greatly appreciate any advice on how to fix this problem.