problem JDBC driver

Dear Madam, Sir

I am trying to connect a postgresql data via orion server.
So in orion I configure xml config files required.
I have postgresql.jar and jdbcdriver jdbc7.1-1.2.jar

when I start orion server I have always a message :
" error initializing data-source : jdbc/PostgresDSCore : DriverManagerDataSource
driver 'org.postgresql.Driver' not found

I have changed jdbc driver, but error message still displayed
I have verified my data-source.xml, postgresql.xml , server.xml and
application.xml : from web sites and seems ok in orion
I searched information on google engine and tried a lot of things, but the
problem is the same

could you help me or give me advice ?

I use :
postgresql v7.2.1
cygwin + cygipc (ok)
orion : 1.5.2 (in order to develop JSP and servlet)
windows 2000
jdk 1.3
jdbc driver 7.1-1.1 then 7.1-1.2 then pgjdbc1 and pgjdbc2 all jar files

I cannot go on with my work
more thanks in advance

marie-paule torre