I have an M-Audio Fast Track Pro (MAFTP) running on a Windows 7 64-bit OS with an 3.4 GHz i-3 processor and 8 Gb of RAM. Yet usually when I run any sort of audio through the MAFTP I get serious lag with cracking and popping sounds. When I watch a Youtube video the video will lag as well.
This is sometimes fixed by unplugging the MAFTP and unplugging my Pro Tools MP-9 dongle, but that's becoming a less and less reliable work around. My computer is plenty fast and this happens even if I'm just playing audio through windows player.