Recently my XP Home Edition has often not completed the shut-down properly -- it hangs on the 'Windows is shutting down' screen. When I restart next day, having switched off using the power button, it usually goes through the chkdsk routine, but not always. This seems to happen irrespective of what software I've been using -- the last couple of times I'd only played a couple of games of Spider Solitaire!
PC is Athlon 600Mhz with 256Mb memory. I use an up-to-date AVG, Kerio firewall, plus Adaware and Spybot.