Today when using my PC as I did for almost 4 years I experienced the following: during opening new tab in Opera browser screen froze. Music (AIMP 3) continued to play for about 5 minutes and then stopped too. I tried Ctrl+Alt+Del, but win7 lock screen didn't appear. Caps\Scroll or Num locks didn't switch diodes on keyboard. I rebooted my PC and saw that BIOS suggests me to enter it's settings or load by default. I chose default. It don't see proper boot device (old faitful "insert proper boot" something). After second reboot it said that there is no ExpressGate installed (which i turned off in BIOS years ago). I went into BIOS setting to turn off ExpressGate and see configs: time was not set off, all hard drives present, temp and O.C. settings are nominal (no O.C.) I've inserted my Win7 install disk to try recovery. It did load awfully long (about few minutes) and didn't see current installation. PC was utilized in 24/7 mode for almost all these years. Hardware configuration: ASUS P5Q WS Core 2 Quad Q9300 (2.5GHz no O.C.) MSI geForce GTX 460 4x2 Gb GeIL EVO 2 (AFAIR) Seagate something 750Gb (4 years as system HDD 24/7) WD 1Tb (for random stuff, 5 y.o.) Hitachi 500Gb (for even more random stuff, 6 y.o.) NEC DVDRW (ALL DISKS ARE SATA) Cooler Master Silent Pro 700W Software: Windows 7 AND Kubuntu on the same drive with GRUB loader. Sorry I can't remember HDDs and can't see them right now, but I think their models aren't relevant anyway. My idea is that due to some system error or hard drive glitch i've wrecked my primary HDD's MBR. Nevertheless I don't exclude the possibility of other failure. May it's be that motherboard or it's SATA controller? Doubt it, because all drives are seen in BIOS and I could load from DVD. Maybe GRUB got bugged somehow, although I don't see how it's possible from Windows. But I did install KUbuntu from Windows (i wasn't myself then), maybe GRUB did write itself in some windows partition and got rewriteen in process? Right now I am at work with my flash drive with me and I need some advice how to fix MBR or to hear if it's not MBR. I'm going to buy new HDD (Hitachi 7k2000) because I think that my current HDD is compromised and it's unsafe to use it as system drive, especially 24/7.