Well, you could run various versions of Linux and then there are several open Office varieties that will load and save MS Office files. I am not certain how Wine (a limited Linux single app emulation of Windows) will do with running the latest version of MS Office but it's worth a try.
The real problem is all the specialty vertical solution software out there that will only work on Windows. It is highly unlikely to work on Linux even under Wine. There you'd have to use something Apple's OS X on a Mac running a virtual machine running a single instance of Windows just to run the vertical solution software ONLY in a sandbox, not allowed to connect to the Internet, leaving all else on the Mac side. You could try building a Hackintosh on your PC hardware, but only certain configurations of PCs are capable of being converted to Hackintoshes.
I did get a couple of android tablets and downloaded a version for droid that opens and saves MS. My have to do that.
I am not so keen on giving the socialist Gates all my information without my permission.
The other possibility, if he has PC hardware but not Mac hardware, is to run Linux on the hardware, and run a Windows virtual machine on that. I personally prefer the free Xen VM hypervisor, but less techie-intense, free solutions are available such as Virtual Box.