network utilization from 64 bit vista to32 bit vista

I am seeing extremely poor network utilization when I copy a file from a 32
bit vista to a 64 bit vista machine, but excellent utilization when I copy a
file from 32 bit vista to a 32 bit vista.
32 bit vista to 32 bit vista file copy -> network utilization is > 90%
32 bit vista to 64 bit vista file copy -> network utilization is < 10%

Do I need to set certain settings to get this working better.