When upgrading from Microsoft Office 2003 to the 2007 release you should not need to upgrade your hardware, although you may need to upgrade to a supported operating system. When upgrading from Microsoft Office 2000 or Office XP to the 2007 release you will need to ensure that your hardware and operating system meet the minimum 2007 Microsoft Office system requirements.
We highly recommend you evaluate your computer before installing 2007 Microsoft Office system products to verify your computer meets or exceeds the minimum system requirements.
2007 Microsoft Office system programs are supported on Windows Vista Beta 2 (when available), and not earlier versions of Windows Vista. The 2007 Microsoft Office system programs client is a 32-bit application and runs on a Windows 64-bit platform (Windows XP and Windows Server 2003) via WOW64.
Computer and processor - 500 megahertz (MHz) processor or higher
Memory - 256 megabyte (MB) RAM or higher
Hard disk - 1 gigabyte (GB); a portion of this disk space will be freed after installation if the original download package is removed from the hard drive
Drive - CD-ROM or DVD drive
Display - 1024x768 or higher resolution monitor
Operating system - Microsoft Windows(R) XP with Service Pack (SP) 2, Windows Server(R) 2003 with SP1, or later operating system
Other:-
Integration with Windows SharePoint Services requires connectivity to Microsoft Office SharePoint Server 2007 or Windows SharePoint Services 3.0. Built-in InfoPath Forms Tool requires Microsoft Office InfoPath 2007. Groove/messenger integration requires Windows Messenger 5.1 or later or Communicator 1.0 or later. Includes a 1 year subscription to the Groove relay service
Internet Explorer 6.0 or later, 32 bit browser only. Internet functionality requires Internet access (fees may apply)
Additional - Actual requirements and product functionality may vary based on your system configuration and operating system.