Here is an extract from MS Office specs: "Operating system: Windows XP with Service Pack (SP) 3 (32-bit operating system (OS) only) or Windows Vista with SP1, Windows 7, Windows Server 2003 R2 with MSXML 6.0, Windows Server 2008, or later 32- or 64-bit OS."
I have MS Office 2007 as well as MS Office 2010 on different computers. Both install and run fine on 32-bit as well as 64-bit OS computers.