I HAVE THE SAME ISSUE! Disk is at 100% usage latency always 900-2000ms on the performance tab of task manager. On processes tab it only shows roughly 40% consistently high is still pretty high. Running on an I7 3630qm 8gb ram clean clean install as in the "extensive" format and reinstall of windows 8 from the settings General- remove everything and reinstall windows. Took roughly 8-10 hours. If it helps i am also unable to access bios without removing my primary HDD and pushing F2. This only started after i went back to win 7. Then went back to win 8. Both clean installs same issue on both causing bad lag and performance.