Margaret T. wants to boot from a flash drive and work on documents from there.
You'll need to get an operating system onto the flash drive. You've got a number of options, and I'll discuss two. But first, a couple of rules that apply to any bootable flash drive:
1) Make sure your PC can boot from a flash drive. You can do this in the hardware settings (also called the CMOS or BIOS settings), but I can't tell you exactly how. Boot your computer and look for a message like "Press KEY for Setup." It will be one of the first things to appear on your screen as you power up. Press that key immediately. Hunt the resulting menu for something like Boot Options or Boot Order. You want to make sure that USB devices are listed before your hard drive in the boot order.
2) Use an empty flashdrive. It will make everything easier.
When you're ready to create a bootable flashdrive, I recommend Ubuntu Linux as your operating system. It's lighter and faster than Windows, it's free, and it will give you a chance to try something new. It won't run Microsoft Office, but there are plenty of Office alternatives that run just fine in Linux, and it comes with one of them: OpenOffice.
One other advantage: Creating a Ubuntu boot flashdrive is surprisingly easy.
You can download Ubuntu here, but be patient. It's a big file; over 700MB. It's also an .iso file, which is basically a disc image. There's a good chance that when you double-click it, it will open up a program that will burn the file's contents to a CD. If that doesn't happen, download and install ISO Recorder, then try again.
Once you've got it burned to CD, boot your PC with that CD in the drive, wait a few minutes, and you'll be booted into Umbuntu Linux. Then select System • Administration • Create a USB startup disk. It's all pretty simple from there.
But what if you don't want to learn Linux? What if you want to stick with what you know--Microsoft Windows and Office?
In theory, it's impossible to install Windows XP or Vista onto a flashdrive. But someone figured out a way to do it with XP. The procedure is very long and complex, but you'll find detailed instructions in this TechRepublic article.
I'll confess right now: I haven't actually tried this. Just reading the instructions inspired me to stick to Ubuntu. But when Margaret T. posted the original question on the Answer Line Forum, smax013 recommended this as the solution. Margaret thanked him and marked her question as answered.