how to create backup copies

I created a bat file mybackup.bat

set FAILINIMI=%DATE:~8,4%%DATE:~5,2%%DATE:~2,2%eevavarukoopia.backup
"C:\Program Files\pgAdmin III\1.4\pg_dump.exe" -i -Z9 -b -v -f
"C:\mydir\%FAILINIMI%" -F c -h localhost -U postgres mydb

and verified it using RUNAS that it runs OK under posgres account.

I entered c:\mydir\mycackup.bat

to a pgagent script window

however, statitics window displays the following error each time I try to
run this job:

Couldn't execute script C:DOCUME~1\postgres\LOCAL~1TemppgaD591.tmp1_1.bat

any idea how to create backups automatically every night ?

Environment:

Postgres 8.1.3
PgAdmin 1.4.2
Windows 2000 server

Andrus.