In case you still haven't heard, the death of Windows XP is just around the corner. As of April 8, 2014, Microsoft will no longer being providing any support for XP. What does this mean? It means if someone discovers a gaping security flaw after April 8, 2014, Microsoft is not going to fix it. As a practical matter, running XP may be like opening your front door and inviting the burglars in. If you haven't done so, you should upgrade your XP machines.
But what about those older machines that have XP on them, are still plugging away, but don't meet the minimum requirements for Windows 8? You could simply give them up as a loss, and I don't think there is anything wrong with that.
However, you can still breathe fresh life into those old machines. As an example, I had a ten year old Dell Laptop that my wife had when she was in college. It had XP on it and was a bit sluggish. But it was a good machine in its day and still had some life it. Yet, Windows 7 would not have been an option, let alone Windows 8.
Instead of consigning it to the trash heap, I changed operating systems entirely and started looking at Linux. More precisely, I installed Linux Mint 13 with the Mate desktop and completely erased the old XP system. This distribution of Linux is 100% free and its authors are providing long term support until April 2017.
It has a feel that is not completely foreign to XP, though there is some amount of learning necessary. There are numerous resources out there to help people make the switch from Windows to Linux, and even resources on how to make Mint look like Windows.
Additionally, some of the software you need for practicing law can be had for free in linux. For example, LibreOffice is a free office suite comprable to Microsoft Office's products. A little use of Google can help you find what you're looking for.
There are, of course, some downsides. Windows specific applications may not be able to run on a linux machine. Additionally, you might have to spend some more time in the command line than you would like.
However, if you are looking to get a little extra life from your older machines currently running XP and are willing to try something new, then you should give Linux a look.