not gonna lie this is driving me nuts something is choking my PC. Loading screens take forever, textures pop in late, and a racing game stutters constantly. Task Manager:

Disk 0 (C:) Active time 100%
Not responding
100% disk, and the response time numbers look scary. i suspect Windows Update, but i'm not sure how to prove it.
I already restarted the PC and closed everything I could find in the system tray. Disk usage dropped for a moment, then went straight back up as soon as the game loaded a new area. any ideas??