As a private-practice attorney, my father has typically had the most powerful computer in our family. Years ago, when my family was using a donated 286 with MS-DOS 5.0, my dad purchased a 486 with Windows 3.1. He wouldn't let me or my brothers play Klondike solitaire on it, though - we might break something!
One thing that has stayed constant, however, is his use of Corel Wordperfect. For whatever reason, many lawyers in town standardized themselves to Corel's products instead of Microsoft Office. From Wordperfect 6 for MS-DOS to Wordperfect X3 for Windows XP, my dad has kept abreast of newer hardware and software in order to interoperate with the documents sent him by other attorneys. Now, 15 years on, the county court system has standardized on PDF documents for online submissions and publications, which meant another round of upgrades and purchases - the only software that can directly edit PDF files costs several hundred dollars, and required an upgrade from Windows 98 to Windows XP. That in itself required a hardware upgrade.
My dad has been on a costly upgrade treadmill for many years, and now the question remains: what becomes of his documents from the past 15 years? They're all stored in a proprietary format that has changed several times over the years, and there's no way to mass convert a decade and a half of documents into a usable format. It is guaranteed that those documents will one day be completely unreadable.
Even Microsoft Office documents are subject to this problem. Microsoft has put on a show to demonstrate that they're all about openness, but their (literally) 6,000 page specification is replete with implementation landmines. Preliminary research has unearthed many, many pieces in the specification that make outside implementation an impossibility.
Never, ever settle for proprietary or patented formats and specifications. Your data should never be subject to unreadability, whether it's because a company goes out of business or stops supporting a product, or because you're not using a supported application or operating system. Unfortunately, you're pretty much guaranteed to be using proprietary formats. For this reason, I'll post more later about the proprietary formats and specifications you're most likely to be using.
[MS-DOS]: Microsoft Disk Operating System [XP]: experience *[PDF]: Portable Document Format