Repair Master Boot Record?
October 6, 2013 8:33 AM   Subscribe

I have a Windows 7 HTPC that serves as our family's TV/entertainment hub. Recently, the cooling fan on it died a slow death while I wasn't home. The other folks in my home kept re-sarting the machine frantically, until I ended up with multiple drives with (I believe) damaged Master Boot Records. How do I fix this?

One of the damaged drives is the main C: drive. That one won't boot now. The other two are external TV/movie archives that will load, with complete file listings that show file sizes for everything as 0 KB.

I have a laptop I can use to help recover things, a dock that will let me load the internal C: drive as an external, and an extra 1 TB drive I can use to move things around.

How hosed am I? What should I try to recover things?
posted by DirtyOldTown to Technology (3 answers total)
First thing is to commit to not connecting the damaged drives to anything that's going to try to write to them.

Second thing is that it's probably not worth attempting to recover the b0rked Windows installation. Just recover as much of your media collection onto fresh drives as you can, then start over with a fresh Windows installation.

The tool I've had success with for this kind of job is Zero Assumption Recovery. It's trialware - there's a free demo version you can use to recover the contents of a limited number of folders. You can do that repeatedly and get all your stuff back piecewise if you're into extreme tedium, but if it looks like it's going to work for you, $60 is reasonable for what it does.

If you think the damaged drives could have overheated due to the lost fan, you should replace them. But if all that's happened is soft corruption from being connected to a dying computer, then after extracting as much as ZAR will get from them, they should be OK to repartition, reformat and reuse.
posted by flabdablet at 8:52 AM on October 6, 2013 [1 favorite]

If it really is the MBR which is broken you can fix this by starting the computer (the broken one) from a Windows 7 installation DVD (or USB dongle), then instead of installing it choose "Repair my computer", and select the command line. From the command line you can type BootRec.exe /fixmbr to change the MBR to boot from the installed Windows found by the DVD.

There are also a couple of other options to bootrec.exe which might make the drive boot again, and there is an automatic procedure which might work as well.

IMHO it is more likely that you've got read errors on the C: drive, so you should also do a full scan for errors - doing something like this. (The reason I think that is that the MBR is very rarely written to, it is just 446 bytes in the beginning of the disk) This you can of course do from the laptop using the dock.

I've with luck used free software such as gddrescue (on Linux) to copy partitions with broken Windows installations to another disk, then fixed the MBR, then resized the partition with gparted, but that is slightly more advanced - there might be some good guides out there if you're willing to spend the time thought.

If you have files you want to save from the disk you should try to copy them from the disk before doing any of this.
posted by Baron Humbert von Gikkingen at 10:06 AM on October 6, 2013 [1 favorite]

Currently dealing with the same issue with testdisk. Redoing the mbr didn't work for me, but it also allows you to copy files! It's a command line tool, but it works freaking great... Although tediously.

If you have a big enough destination drive you can just go "select all>copy" with the destination punched in.

Note: this requires either a Linux boot disk or a Mac, and some knowledge of how to navigate the command line on a unix-ish platform, mostly to find the actual(disk3s2 type of id) info for your damaged drive and the mount point of the destination drive for the files. It isn't advanced stuff, but look up testdisk guides if that wiki doesn't cover it enough.
posted by emptythought at 11:47 AM on October 6, 2013 [1 favorite]

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