I received this how to in my email a couple of days ago from colleague Daniel Langenhan. Daniel was so kind to let my share this with you. If you are looking into installing vCenter on Windows 2008 with an Oracle database this might come in handy:

1. Download 32bit Oracle client (even on a 64 bit system). Oracle 9i is not supported and the installer actually checks that. You only can use 10 or 11″.
2. (10g) Download patch 5699495
3. Install the 32 bit client using full Admin mode
4. Use Net Manager to setup connection to Oracle server and test
5. Use 32 bit ODBC [windows]/sysWOW64/obdcad32.exe
   The 64 bit is the one that shows up in Administrative tools and the installer will not use this.
6. Create system DSN’s and test connection
   (10g) if error pop up doing so the patch from step 2 was not installed