PIC's and USB

[Randy Day]

I downloaded some stuff on how to use
USB from:

http://pe.ece.olin.edu/ece/projects.html

I want to make a PIC act as an HID
keyboard, but I've come up with a couple
questions before I get too deep into this.

1) Most of the schematics I see show an
external xtal running the clock; is this
necessary. or is the onboard clock
adequate for short data xfers?

2) Prof. Minch's code simply keeps sending
the same text over and over. What's the
simplest way to have the computer send a
char to the PIC saying 'OK, send me the
next batch!'.

Thanks. This stuff is like trying to
swallow an elephant!