Problem upgrading from php3 to php4

I'm continuing to have problems upgrading from php3 to php4. I have both versions installed on WINNT w/ IIS3.. When php3 is enabled (ie. when I have php3.ini in WINNT and no other php.ini file in WINNT), php works fine. But when I replace php3.ini with the php4 version of the ini file (named php.ini), I cannot get passed the "Unable to parse configuration file" error message. I have php3 installed in C:\php and php4 installed in D:\php. I updated the extension-dir line of the php4 version of php.ini to point to D:\php (even though I'm only using the built-in ODBC extension, so I wouldn't have thought that would even be necessary). Also, I moved php4ts.dll to the WINNT/SYSTEM32 directory. But still can't get passed the error message. Thanks in advance for any information that might help fix my problem. Lenny Harris