Switching to Windows doesn't mean you're forced to use a simple text file or Excel spreadsheet, there are plenty of alternatives out there. I'd suggest a web-based system such as Remember The Milk, Nirvana, or ToodleDo, as they're accessible from any operating system or location (as long as you have Internet access). That would also allow you to manage home and work in the same GTD system (as there's no need to have separate home and work systems in GTD--both have related tasks, they're just in different contexts).

However, if you need to use a simple Word or Excel document, it should be fairly easy to set up a collection of lists (inbox, next actions, someday/maybe, waiting, etc.). In Excel, you could have a worksheet for each. Contexts could be tracked in a separate column, so you could easily sort by context.

Or you could implement a more advanced system like the one J.T. Hurley shared above. But in my opinion, that's just reinventing the wheel. Better to use an existing system (under active development to add new features) than to make your own from scratch.