RayC - Did anyone ever mention MacOS's Bootcamp to you? With VMware Fusion or Parallels, you're working within a virtual system, but if you're dealing with large database files, that could drive you crazy. Assuming that you can work within an Access file without drawing upon a number of Mac files, you can start up your Mac in Bootcamp, install whichever flavor of Windows OS upgrade (for licensing, MS legally views an OS install on a Mac as an "upgrade") you want, and it will run very well. In addition, if you keep that Bootcamp's software installation super-stripped down, you'll find performance will be optimized for that single task.
The beauty of Bootcamp setup on the Mac is that you don't have to do manual partitioning. It's very easy, though if you're feeling uncertain, you can make an Apple genius bar appointment for help.
I have disliked the corporate decisions to use Access (or any single-platform app). It's been a clunky, rather ugly app. However, maybe it's improved its esthetic and functional qualities since I last used it years ago.