i had this problem also with win7, i installed xp over the top keeping all my files and now boot to xp and its all fixed and running faster and better than ever. I recon this model works better with xp. i also dj and now i have no lag or problems using traktor.
i installed windows 7 and went back to xp, the drivers work better for xp as the win7 drivers are pretty much vista drivers. stick with xp, theres no advantages with win7.
There can be issues with the audio driver.. i tried the few versions of vista drivers available (as there are no win7 ones) and put up with crackly audio that was so bad on some movies and youtubes it made it impossible to use so eventually i installed a good version of xp pro sp3 and installed the ...
if you install realtek hd audio manager audio driver version 5.10.0.5464 then when you plug in anything a popup box will appear and ask you if you want headphones or speakers. hopefully this will fix it