I'm still using an 11 year old XP-based desktop PC. The only problem with it is that the onboard graphics are not fast enough to cope with HD videos. I installed a PCI graphics card to try and fix that but it didn't make any difference. I reckon the 1.2 GHz Athlon can't get data to the card fast enough. I can use my laptop to watch videos, but it is a bit of a nuisance having to switch it on just for that.
Still, apart from slow graphics performamance, the old PC is fine. I'll keep using it until WIN XP support is stopped and will probably then stick Linux on it.