My PC is 3.5 years now. It's been great but it's time to get an upgrade. What's holding me back is Windows Vista. The horror stories continue and now with the Windows 7 talk there's some evidence that Vista may be a dead end and XP -> 7 is the upgrade path.
Any advice? Comment here or email me. I actually like XP once you turn off the Aqua graphics nonsense. My PC spends 95% of its time running Firefox, Thunderbird, PuTTY, and games (mostly Warcraft). If it weren't for the games I wouldn't even bother upgrading. Arguments for Vista: DirectX 10, multimedia which requires DRM, and inevitability of the OS.
PS: if you tell me "buy a Mac" I will publically mock you. I don't want MacOS.