PHP over Win2003 IIS problem with oracle "accents& ñ"

I have a problem trying to insert data with "accents" and "ñ" into an oracle server from a php application running over windows 2003 and IIS 6 PHP 5.2.5 Zend Core for Oracle v2.5, when I insert from this server the data base shows simbols instead of "accents" an "ñ". My Oracle server 10g XE is also running in windows 2003.

I have an other PHP 5.2.5 Zend Core for Oracle v2.5 testing server runing over Windows XP with IIS 5.1 connecting to the same Oracle server. When I insert from this XP server the data base shows the "accents" and "ñ" correct.

The data base is the same but i got different results from 2 php server in different OS, both are in english with the same Regional and Language options..

I try:
- Use the utf8_encode() when insert,
- Use the utf8_decode when insert,
- Use the header('Content-type: text/html; charset=utf-8') in the first line of the PHP code,
and header('Content-type: text/html; charset=iso-8859-1')
- I try to set the default_charset to iso-8859-1 and UTF-8 in the php.ini file
- When specify the charset in the oracle connection from php to AL32UTF8 example:oci_connect($ora_user,$ora_pass,$ora_host,'AL32UTF8');
- Change Regional Setting to spanish
- I change the NLS_LANG to "MEXICAN SPANISH_MEXICO.WE8MSWIN1252" in the registry of the Oracle server
- Print the accents and ñ direct into the query to avoid strage conversions in the post or get transicion, this for testing purposes

Why having almost the same configuration the XP insert fine and the Windows 2003 no?

What other things I can check?, I don´t have any other idea where to check.

I hope some body can help me.
THank you