Yet another test is how badly we can hurt a computer. I actually did this several years ago, when Windows 95 came out, and and I wanted to see what all the hubbub was about.
So, one Saturday morning in late '95 I got the CD, popped it in and tried. The machine it was running on was:
The Install happened while I was out mowing the lawn. This took about 60 minutes to do, and when I came in, it was at 40% completion. I had cut the installed options down to a bare minimum, but I guess it still had a lot of data to copy. I left it and rode my bike somewhere.
When I returned some time later, it was ready to go. The 4 meg of RAM is had was basically enough to just get the Virtual Memory system running, so the entire system was running off swap.
Cold-Booting the system to a usable state took about 7 minutes. The Start Menu took about 20 seconds of disk access to display, and starting up Netscape Navigator 1.1 took about 2 minutes. You don't even want to know how long it took for Word Perfect for Windows took.
You think this is bad? Once, me and a friend once managed to get Windows NT 3.5 running on a 386sx/16...
Why on earth am I telling you this? To illustrate the point that system requirements put forth my many companies are lying documents that are not worth the dead-tree carcas they're printed on. With the exception of games, hardware requirements are, by and large, hardware suggestions with the exceptions of drive space and architecture requirements (e.g. 16-bit vs. 32-bit).
In this case there was no reason that I couldn't use a 386 because even though the manual said it required a 486, we all know damn well that there is nothing so different from a 386 to a 486 that would be show stopping.
In all but a few cases, then, Hardware requirements == Hardware Suggestions. A Pentium 4 may be a metric assload faster than a 386, but there is almost nothing (save SSE/MMX) that the Pentium can do that a 386 can't do, just a hell of a lot slower. Granted that you won't have the "user experience" they talk about, but it will work. This is a tenent of good design.
Except now, for Microsoft.
Starting with Windows 2000, when they said you needed a minumin of a Pentium 100, they were serious -- not because there are any features that require it, but because they check for it, and it won't install without it.