I tried to OC my system this morning, and now Windows isn't booting. I have a GA-P55M-UD2 motherboard (BIOS ver F11) and an i5-750 CPU. The only settings I changed was to disable the turbo boost then set the BCLK to 160 (to take the CPU to 3.2GHz). After saving and rebooting, Windows failed to boot. It got to the black Win 7 splash screen (with the glowing Windows logo) then it restarted. As I had backed up my settings before the OC, I restored these settings and restarted. However, Windows still failed to boot same as before. Safe mode also failed to boot, and when I go into the system repair options it fails to recognise any installed operating systems to I can't system restore or anything else. I guess I have to re-install Windows now, but does anyone have any suggestions for what I might have done wrong or things to check before I do this? I was also wondering what I should set the SATA controller mode to? I have a Samsung Spinpoint F3 SATA drive. I'm pretty sure it was set to ACHI mode before I changed anything, but when going into the standard CMOS settings screen my HD and DVD drive (both are SATA drives) show up. They only show up when the SATA controller is set to IDE. I assume this is normal? Thanks for any advice!