What have you found to be the least expensive portable computer that will handle Microsoft Word? I don't need any other Office applications or the internet; however, I do need either a USB connection or a CD drive so I can save my work and take it to a printer.
The minimum writing computer today is an iPad mini 2 with a Bluetooth keyboard, which you can get for about $300 total. It is basically a digital typewriter.
Key advantages over a traditional PC:
it is mobile and has 10 hour battery, so you can take it everywhere with you so that you can write whenever and wherever inspiration strikes
you can choose from literally thousands of Bluetooth keyboards, either generic ones or ones that are made specifically for iPad, and that enables you to choose one that really suits your taste, as opposed to just using whatever keyboard is built-into a cheap notebook or came with a cheap desktop
there are writing apps for iPad that are totally focused on writing, and are much better for a writer than Microsoft Word, with less distractions, auto-save, auto-backup, beautiful text rendering, and they cost $0 to $10 each — but if you specifically need Microsoft Word, it runs on iPad also
there are great note-taking and outlining tools, again that are only $0 to $10
there are great native blogging tools, so that you can very easily manage a blog to go with your writing, and these are typically free
your writing apps run full screen by default (although you can bring a second app out from the side) so that you are really focused on your writing, like with a typewriter — the default style is like Kerouac’s typewriter with teletype paper in it: a giant endless page that you can type into without distraction
iPad backs itself up to the cloud, so you don’t need to work with disks or USB keys to do that — although there are USB keys with both USB and Lightning that work with iPad
there are apps for sending print jobs directly to printers over the Internet — for example there is one that you can use to send a print job to a FedEx Office and then you go to the FedEx Office location and put a code into a photocopier and your print job comes out
you spend less time working with the computer, troubleshooting it, using USB keys, backing it up, and so on, and therefore you get more time and focus for your writing.
Today, ideally you don’t go to a computer or lug a computer around, and you don’t use sneakernet with USB keys — you just have writing tools in a backpack or briefcase or purse that you can use at any time and which can send print jobs over the Internet and back themselves up over the Internet.
As Tave says in a comment, to get an authoritative answer you could go to the Microsoft website, check the system requirements for MS Word, and then go to any website that sells computers and look for something meeting those requirements.
In practice, with the current state of technology, MS Word is a pretty light load for a modern computer. If that's all you plan to run on it, I think almost any current generation computer would do the trick. I'd suggest you consider what size keyboard and display you want.
I think you'd have little trouble finding a low-end laptop adequate to the job for under $300.