allpccamera USB for webcams. I found this driver in China (made by '10 moons').
I've used it 3 times with ancient no-name web cameras whose drivers are unobtainable elsewhere. It has worked for me every time with XP.
When installed it'll put an 'Amcap' program into your computer (just look in all programs ..). To install just open the zipped file and double click on the setup.exe
45Mb download - but maybe it'll be of use if you can't find drivers elsewhere.