I have a Windows machine sitting on the other side of my room, safely segregated from my working desk. I use it for work purposes occasionally: to deal with legacy files and to test stuff in IE, plus I play a few games now and then, and I prefer to keep them compartmentalized away from my work machines. Sometimes I use VNC to connect to it so I can play online poker from my Powerbook
Before I started using Macs -- and, really, before I started using OS X -- I think I actually enjoyed fooling around with Windows, to a degree. There used to be some level of fun in installing new video drivers to make performance just a little bit better, and in running all sorts of little applications to tweak my computer. Once I learned that doing stuff with the computer was cooler than doing stuff to the computer, I began to resent the never-ending stream of maintenance that Windows seems to require: relatively frequent security updates, virus scans [and updating the software and definitions], spyware scans [and updating there, too], defragging, and as many hardcore users will say, a full reinstall roughly every year.
I don't have time for that. More importantly, I don't want to spend that much time doing "work" to maintain a computer that doesn't do much work for me -- time I spend twizzling with Windows is time I can't spend on something more profitable, constructive, or fun.
I bought the current Windows machine [a HP, it has an AMD processor, some RAM, and perhaps a very small donkey inside] in late 2004. I've been faithfully upgrading my virus scanner, my adware scanner, and I defrag it on a regular basis. I'm such a good little babysitter. I've never had a virus on that machine, never had "adware" more intrusive than a cookie, and all in all, the machine is still pretty stable [although slower than it used to be ... something about "using it" that seems to make it slower.]
As of now, though, I'm stopping. I've set the virus scanner to run once a month, and to check for updates on the same schedule. I'm not going to run spyware scanning software out of habit anymore -- only if I suspect Windows has become crudded up. I'll upgrade the software firewall if it stops working for some reason or if I run into some sort of incompatibility, but I'm not going to touch it otherwise. Defragging? No. Scandisk? Only if I have reason to suspect the hard drive is failing. Windows Updates? Once a month, no more. I've turned off auto-updating in Firefox -- the version I have works, and I have extensions installed that work. I'll update them once a month if there are updates available. I am not even bothering to check if I could install Vista on it.
I'm going to set this up on a schedule: first Saturday of every month is "the day I am allowed to spend an hour -- maybe two -- dorking with Windows."
At some point during the year I'm going to transfer as much of possible of the actual data on the drive onto an external drive, and back static data up onto DVDs. I'll keep the external drive powered off unless I'm actively using it.
With minimal babysitting and sane browsing habits, I think there's a fine chance of the computer staying relatively clean and useful for another year or two. At that point, it can go in the garbage and be replaced -- or not -- and I'll feel fine about discarding something that I have so little investment in, and no valuable data on.