OCModshop posted a guide about optimizing USB Drive Performance in Windows Vista

Another one of our articles shows you how to speed up SATA hard drive performance in Windows Vista by enabling advanced write caching. A similar performance tweak can increase USB drive performance, by using more system memory as a write cache, which significantly increases performance when writing to the disk.

Flash-based USB devices can benefit greatly from this tweak, as many of these drives peak at a 6 or 7-megabyte per second write speed. The storage capacities of today's flash drives are measured by the gigabyte, so filling up an 8GB or 16GB drive can be a long process. This tweak won't magically make the silicon in the drive work faster, so copying 8GB of MP3s will take just as long from start to finish with or without this tweak. Relative drive performance improves by making the device available sooner for other processes, like when you're using portable applications on the device or transferring small batches of files.

Optimize USB Drive Performance in Vista