Warning, long post ahead.
But I feel like it's my obligation to dedicate a post to the most annoying XP problem I've ever had. Like, seriously. The most annoying.
EVER.
Some time ago (like, some months ago), my computer decided to go totally stupid on me and stop installing new USB devices... eg. regular old USB flash memories of the kind that even stone-age computers with XP can recognise and use with minimal work (the definition of which does not include "installation") on the part of the user. Upon plugging in a USB drive, my computer would recognise it, throw up the "add new hardware wizard", mess about for a few minutes and then completely fail to install anything.
Thing is, there seemed to be no real hardware problem. My old ipod shuffle worked just fine, as did my USB mouse. But I could add nothing new (how like life

).
Updating windows didn't help (curiously enough, my computer had been completely unable to update windows for a very long time despite continually downloading and "installing" the updates). Uninstalling the USB devices, no help. Repair XP? Ha.
Today a little angel went and bought me a handy 8 GB USB drive. I thought that perhaps things had changed since I finally coaxed my comp into getting SP3, but when I stuck it in, I realised my curse was still upon me.
So I got mad and took to google... and learned two things:
1. I wasn't alone. Thousands of people have had this same problem.
2. There didn't seem to be any good working solutions that didn't involve reinstallation of XP. No-one seemed to be in the know.
It was way past my bedtime, but I'd decided that I wasn't gonna go to bed until I'd solved my problem (and posted about my success

). Google had let me down a little, but I persevered and finally chanced across the solution:
Incidentally, the paths that XP searches during a plug'n'play installation are defined
in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DevicePath
Good call Martin..
After inspecting the registry key and cross-referencing it to another machine I found that it was all jacked up.
The default entry for this key appears to be '%SystemRoot%\inf'
However, the entry on the problematic machine was set to dozens of invalid paths..
It looks like this, '\inf;\drivers\USBMouse;\drivers\Stick;\drivers\Wlan;' and so on. I deleted all this without prejudice and inserted the default entry, then rebooted.
Thanks.. The problems is now solved.
I went and took a look, and found the signs of Satan's work in my registry. I cleansed it, and,
voila, problem solved.
I have performed the mandatory jig, and now all I want to do is spread the knowledge so that other victims can also help themselves.
Perhaps one day one of your machines will turn on you in a similar fashion. On that day, I hope you will quickly recall this thread, and thus avoid prolonged suffering.
Until then, rejoice with Aimy. And weep a little with him for his pitiful discipline, ffs he shoulda been in bed sleeping hours ago

PS. It might be time for a reinstall.