Postgres installation problem

Hi all
I have installed the postgresq 8.0 as a program in C:\PostgreSQL\8.0. I have also set the ENV varibale PGDATA as "C:\PostgreSQL\8.0\share" for the postgre.conf file.
when I try to start it from C:\PostgreSQL\8.0\bin\postgres.exe then I am getting the following error:

C:\PostgreSQL\8.0\bin>postgres.exe
FATAL: "C:/PostgreSQL/8.0/share" is not a valid data directory
DETAIL: File "C:/PostgreSQL/8.0/share/PG_VERSION" is missing.

Could you please give some guindance. I thank you in advance.
kader Lattab

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