Hello,
just two small hints:
A) If you compile the USB examples from KEIL (HID and Mass Storage,
both from July 2005) use a up-to-date uVision3 (e.g. 2.32a). I first
use uVision3 version 2.00 (which i installed for LPC2138) and it
compiles fine and runs, but WinXP always told me "unknown USB device".
B) Second problem on my side was, that i feed in various debug output
into the examples, but there looks like to be some time critical code
inside. So again i got "unknown USB device".
Just as hint, because it took me a few days to find these things
out...
Regards,
Martin