Hello, I've seen your answer twice in different forums regarding the disbelief of poor HD transfers. My other computer friend and I have experienced this same problem. Her system even had trouble detecting HDs at various times.
This is what actually takes place. On say a 20gb file transfer of mp3 music, my XP machine might zip thru these files to the new HD in 5 minutes, while the Win7 super computer with Intel Extreme mobo and i7-860 will slog it out in about 13-15 minutes. Gets it done, but no one seems to have a fix for this volkswagen that kicks butt on my Maserati machine. Even goofier, the file transfer time starts out at say 8 minutes, then pokes along, and gradually increases the the time frame instead of decreasing the end date to maybe 15 minutes!!. So far this is the only problem to an otherwise great computer, and many others are foruming this query with no answers whatsoever. MS's answer only sends your computer into a loop of endless restarts. Does the w7 need to be taken out of Aero to perform faster trans rates?
Imho the reason can only be different drives. Or even different HDD controllers. Maybe your chipset drivers are not installed correctly. Ever tried to upgrade them?
Maybe the drive you are moving the files onto is just slower than the drive used on the XP system.
I know it does not help you with your problem but I never experienced different transfer rates by switching from XP to W7 or back.
In fact I still got both OS´ on my PC - THE SAME PC.
If my PC would take that long to transfer such rather small amount of data I´d have formated it already starting over from the scratch. 13 - 15 minutes... for 20 GB thats more than what it takes me to transfer 20 GB to my usb-drive!