I have just discovered my laptop in the morning completely hang up. I tried to restart it, it froze somewhere in the process. Then I tried safe mode, it also froze but now showed me where - the last line was showing "crcdisk.sys" and the HDD LED was constantly on.

What does it mean? Just Windows screwed or a hardware problem? Two days ago I just reactived evaluation period for 2008 Server again.

3 Answers 3


CRCDISK.SYS identifies itself as a "Disk Block Verification Filter Driver" and was written by Microsoft. Presumably, it does some kind of CRC checking on data being read off the disk.

With the volume of problems that I'm seeing being reported "about it" and the lack of official knowledge base articles about it, I have two suppositions:

  • It just happens to be the last driver that loads while the text-mode driver list is displayed on a "safe mode" boot, so people blame it even though a later part of the boot porcess is hanging.

  • It really does hang the boot process because something is going wrong.

Both of these are just suppositions. I'd love to hear from someone who actually knows. Reading the various "fixes" that I've seen posted in forums for "freezes at CRCDISK.SYS" and such, all I find is a lot of "witch doctor" superstitious stuff. I'm not finding where people have put together a reproducible error and resolution case. To that end, I expect that some part of the root causes probably is a transient hardware issue with some people. Given that a wide variety of computers have been reported as having problems "with CRCDISK.SYS", it does also seem likely that some later problem in the boot process could be hanging the machine up while poor CRCDISK.SYS just happens to have its name displayed on the screen and, thus, ends up being the object of peoples ire.

If you haven't booted the W2K8 installation CD in repair mode yet, I would. I'd run CHKDSK against your system volume from there and see if that improves behaviour any.


Your PC doesn't hang at all. The larger the HDD the longer it will take to check your drive for bad sectors. Expect in the order of 5 to 10 hours or more to check. In the process it will mark any sectors as bad as appropriate. If you expect your HDD is physically damaged one way to start the CRC check is to go to the properties of your HDD and ask for a check. If you tick to do a pysical check it will start the process. If your HDD is in use at the time (system drive) the check will start on reboot and appear to hang at crcdisk.sys. It will only do the check if you start in safe mode. If you boot normally the physical check will be skipped but it will possibly do a check on files and folders. In this case if you want to force a check you will have to request again. If the drive is not in use (extra HDD) you will find it is able to check while logged on.

If you haven't requested a check the likely cause is disk corruption (physical damage) to the point that it won't boot except in safe mode. It's best in that scanario to recognise what it's doing and wait until the process has finished as it's trying to repair bad sectors. When finished move on to a system repair method to enable proper booting. Once logged on replace damaged files with sfc etc etc.

  • I've just had exactly this scenario with a Sony laptop and it turns out that the hard disk had developed some bad sectors.
    – Linker3000
    Dec 29, 2010 at 9:12

In my case, Windows Vista was unable to load into normal or any safe modes. It would briefly hang at cscdisk.sys followed by the blue screen of death, then immediately flash for a split second and reboot.

To fix the problem, you will need to set your BIOS to ACHI mode. Accessing this setting will vary per computer make / brand.

On a Toshiba:

  1. At boot screen, press F2 until the BIOS menu appears

  2. Select the Advanced menu by using the left-arrow key

  3. Press Enter to display the options
  4. Select AHCI mode and press Enter
  5. Press F10 to save your settings.
  6. Highlight Yes and press Enter to exit from the BIOS utility

Your computer will reboot and Windows will now boot all the way.


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