System requirements for office 2010 are :
1. Office 2010 will be available in both 32-bit and 64-bit versions. You need not to worry about the version of windows you are using.You would be asked to choose between 32 & 64 @ time of installation.
2. Office 2010 will run on Windows XP SP3, Windows Vista, and Windows 7.
3. You don’t need to replace hardware that is capable of running 2007, it will support Office 2010. Like Windows 7 has demonstrated, MS realize that taking advantage of the hardware you already own is just as important as supporting all the new technology coming out.