There have been known problems with the Pentium 4 and Xeon processors, and the Oracle Universal Installer (OUI). While these problems were mostly specific to Oracle8i, there have been a few issues with the 9i OUI, as well. You could try editing the registry entries HKEY_CURRENT_USER\Environment\TEMP and/or HKEY_CURRENT_USER\Environment\TMP to point to C:\temp or some other writable directory path with no special characters.
If the directory specified by HKEY_CURRENT_USER\Environment\TEMP contains a hash symbol, #, then when the JVM tries to parse the dynamically built CLASSPATH it will fail and be unable to load its core classes. The default directory specified by HKEY_CURRENT_USER\Environment\TEMP is %USERPROFILE%\Local Settings\Temp.
Note that you must be very careful editing registry entries as this may cause other applications to stop working.
This was first published in February 2006