Win PE 2.0 - Slow boot from USB Stick

I'm using a USB 2.0 Stick for booting Win PE 2.0 in my company. Although the
Clients support USB 2.0, it seems that it transfers data with USB 1.1 speed
while booting win PE. The boot process takes more time, than it does when
booting win pe from a CD.

The Clients i tried are all HP Clients. I tried on my computer at home with
a newer mainboard an it booted within seconds.

I read in other forums, that this has to do with the BIOS of the client that
does not support booting with USB 2.0 speed before drivers are beeing
initialized under win pe.

Did anybody experience similar Problems and find a workaround for it? Maybe
it is possible to initialise usb 2.0 drivers before transfering the wim.file
to ram, or something like that.

thanks.