Need to make VM hdd larger

Hi,
I'm running low on disk space for the winXP sp3 VM. I've set it to expand in Config/hardware/hard drive. It doesn't seem to expand. I was originally set at 16 gig. It' now has only 14% left (2gigs) and I can't install another program. I've found other threads about this but am unable to make the answers there work. Is there another way to do this or how can i export this pvm to another install of a VM? I've tried to copy the currant pvm to a large external drive but it won't go. I get a message that says "The item Windows XP.pvm cant be copied because it is too large for the volume's format". (It's 22 gig in size).

Thanks,
Ron