First, you are not addressing Apple in this forum, only other users. Second, Apple can't do anything about it as it is a Windows problem in almost all cases. You have either non-standard USB ports, out of date drivers, or another device or program interfering with USB communications. You will have to debug this yourself (although if you call Apple iPhone support they will help you resolve it).
See
http://support.apple.com/kb/ts1286 and
http://support.apple.com/kb/TS1458.
The key items:
Most recent version of iTunes (7.7.1)
Verify that you have a USB 2 port.
Do not use a USB hub.
Disconnect other USB devices that use power (keyboard/mouse are OK).
Update your USB drivers.