Readyboost can speed up things if you use the same files (medium to large size files) over and over again like system files. I you use a lot of small files and have a lot of I/O, readyboost WILL slow things down significantly since no USB drive in existence can compare to RAM. Another important note, readyboost requires more CPU cycle/cache than a pc with readyboost off. So, readyboost can't compensate an anemic CPU with not enough cache.