ok, so when i had backtrack 4 R2, I couldt Unetbootin it straight to my USB (2 gig)
and now when I try to put Backtrack 5 on, it says files wont fit? iso is 1.80 gigs and my USB holds 1.89 gigs of info.
I had it working earlier (with a KDE distribution)
but had problems (like it wouldnt start up, or it would, it would boot to text, then I would Startx and it wouldnt load the UI)
so I switched to a Gnome distribution (by the way both I took 64 bit on)
now when I put the Gnome edition on my USB drive it says there is no more space in the Casper folder, and that it may lose files if I try to continue (i do by the way)
then i reboot my computer (like normal) and boot from USB.
when I boot from USB it tells me

"make sure no discs or external media is in the drives
Press any key to reboot"

not sure whats going on?