Change is hard. We know that. But seriously, Windows XP was released in late 2001. That was more than a dozen years ago. Forget about dog years, in tech years, that is ancient history. It isn't that XP wasn't good in its day. But its day was long ago.
As of April 8, all of those goodies coming to your PC from Windows Update the second Tuesday of each month, such as security patches, will no longer come to Windows XP. The bad guys may try to write a new batch of exploits to attack the large, and now more vulnerable, population of Windows XP PCs. Don't let your PC, and the network to which it is connected, fall prey to these exploits. Doing so could compromise your confidential firm and client data. Without sounding alarmist, this is serious stuff.
You've waited long enough. If your computer is so old that it runs XP, it is almost certainly obsolete. You will realize huge productivity gains with a new and much faster computer running Windows 7 o 8 (now 8.1). Don't be afraid of Windows 8. It is a fast and reliable operating system. With some tweaks and cheap or no-cost add-ins, you can configure it to look like Windows 7, or even XP.
So order your new computer now. Then take a deep breath and read Part 1 and Part 2 of Affinity consultant John Federico's series of blog posts on transitioning to Windows 8. Another great resource for Windows 8 newbies (and everyone else) is the Windows 8.1 Field Guide, a digital book by Paul Thurrott and Rafael Rivera. It is available in PDF, MOBI and EPUB formats. It will be $2 very well spent and contains an indispensable chapter on configuring Windows 8.1 to work best on a traditional (non-touch) desktop PC, which is how it will be used by most lawyers in their offices.