Windows 7 recently did ran CHKDSK at boot time on my Windows 7 laptop, the HP Pavilion dv6-6135dx. After the system finished checking the disk, on which it did find problems, it rebooted. I then was presented with the following blue screen: STOP c000021a. The initial system process exited with a status of 0x00000000 (0xc0000001, 0x00100778). I have access to a recovery partition with a command prompt and an Ubuntu installation on which I can modify the Windows files. Any help would be greatly appreciated.
Automatic check disk Only happens if the volume is marked with a dirty bit by Windows, so the word automatic is misleading, it only runs "automatically" if severe file system corruption or bad sectors is detected by Windows. More than likely you have a failing hard drive, I would back up your data using a Linux Live boot CD and then replace the hard drive, then use the HP Recovery discs to re-install the OS.
You can run diagnostics on the hard drive to verify a failing hard drive, diagnostics can be accessed in the bios