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Similar to this related question, I came home and found that my media center pc showed this message,
Disk boot failure, insert system disk and press Enter

Before I do anything with the (defective?) harddisk, what are the best first steps I can take to fix this with a minimum of damage?

Normally the machine (Win Vista) is always on and never reboots by itself (Windows auto-updates are disabled too). Something must have caused it to reboot, though I'm sure we didn't have a power outage. The machine can't reboot on that disk, but it will boot on another disk I just plugged in for testing.

I haven't changed anything, or even touched the machine, for several days, and it has been running fine until now. I did replace the power supply some weeks ago, because the old one suddenly stopped working. It has been working fine with the replacement PSU.

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I've unplugged the disk to make sure nothing more happens until I've learned some more. I've plugged in a spare disk and I'm installing Win7 on that, perhaps it will let me take a look at the defective disk. – Torben Gundtofte-Bruun Mar 27 '10 at 21:02
Note: this solution worked for Windows Vista. I'm now using Windows 7 and have now the exact same problem again, but the Checkdisk utility (or command line tool) can't find any errors and doesn't fix the problem. I'd expect that I could boot from the install disc and choose restore, but the install hangs before I get that far! – Torben Gundtofte-Bruun Jul 19 '10 at 21:44

Maybe a silly answer, but make sure there's no USB drive plugged in that the computer is trying to boot from (and of course failing). I had this happen and felt migthy foolish when I figured it out...

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We can rule that out. There's only 1 drive in the system, and nothing is connected via USB. Thanks for the quick suggestion though. – Torben Gundtofte-Bruun Mar 27 '10 at 20:43
Then I would put the old drive in an external enclosure and hopefully rescue any valuable data, then depending on how critical this computer is I would just buy a new drive and do a clean install on that. – David Mar 27 '10 at 20:46
That would also have been my plan. I was hoping that another SuperUser could say how tomake the disk bootable again, so as to avoid a lot of new installation and so on. You know, just fix it. I'm afraid I'm going to have to start fresh instead of fixing... – Torben Gundtofte-Bruun Mar 28 '10 at 6:34
up vote 0 down vote accepted

I solved the problem by booting from another harddisk with Windows and from there running the standard Windows Checkdisk utility on the defective disk with default settings. That was all it took; I removed the replacement harddisk and was able to boot from the proper (now no longer defective) disk as usual.

It did require me to temporarily install a replacement disk and install Windows on that, so it took a while. But it worked - problem solved. I must admit that I still don't know what the problem actually was...

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that message is what the BIOS says when it can't find boot code on the MBR. maybe that was corrupted and just needed a little bit of chkdsk lovin'.... doesn't entirely make sense, but maybe the second-stage bootloader was what was having trouble, which seems more "fixable" by a basic chkdsk. or maybe vista's chkdsk does MBR repairs by default now. – quack quixote Apr 18 '10 at 14:37

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