@Caty
I'm in printer industry, We have major problems with some low level USB drivers in 7, same driver in another 7 computer works fine. (nothing to do with 32 bit 64 bit)
Undocumented behaviour, Cosmic dust, whatever.
I have one 7 computer will not flash Nuvi in preboot even after reload windows, another 3 works fine. "Go Figure"
All XP computers work fine.