Oops... overwrote mbr as FAT32

[Maluno]

I recently replaced a case fan on my desktop after it had been shut off for about 24 hours. When I attempted to boot the computer up, however, I got a message that said a certain file in the system32/drivers directory could not be found, and windows could not boot, (windows XP Pro). I put in my windows disk and tried to repair the installation. I ran a command that was something like "fixboot," and of course, it overwrote my Master boot record with a FAT32 file system. The problem is that I had formatted the drive, installed windows, and been using it for months with the NTFS file system. Now the issue is, whenever I boot the computer up, I get a "Missing NTLDR" message, and it says that windows cannot boot.

Instead, I decided to try a reinstall of windows, while leaving the data on the disk intact, so that I could preserve it. Unfortunately, when I put the windows disc in and select the main partition, and the "convert to NTFS" filesystem option within the installer, I get issues where it says setup cannot continue because the disk is corrupted.

Is there a physical problem with my HDD, and if not, how can I fix my install, or... at least recover my data? (I have all the absolutely critical stuff backed up already, but still there is some important stuff to me...)

 

[xtknight]

I had a problem like this too (I had an NTFS partition with GRUB code in its boot sector). When I ran fixboot, it misdetected this as a FAT12 (floppy) partition and proceeded accordingly. So I ended up with a 10M FAT12 partition on a ~160G drive. Not good. I wish I could dig up my old thread, but I remember I used "testdisk" to fix my partition. I only lost around 10M of data (the first 10M of the partition was overwritten). To my surprise, there does not seem to be a KB by MS on this issue, or if there is I couldn't find it. You'll find many similar instances of this problem online.

The MBR is actually the master boot record, the first sector (512 bytes) of your hard disk. First there's the 446-byte code area where "stage 1" NTLDR (WinNT) or LILO/GRUB (Linux), etc code is stored. There are some 72 bytes after it that contain some padding and the partition table. ( details: http://en.wikipedia.org/wiki/Mbr )

On the other hand, the boot sector, which is what you damaged with fixboot, is the first sector of a given partition. It somehow detected your NTFS partition as FAT, then overwrote the first sector with blank and bogus data, pretty much exactly what it did to my Frankenwindows partition.

First: there are bootable floppy disks for testdisk, so I suggest you try that to recover your partition. You probably shouldn't have done anything after it happened as to maximize the chance of recovering the data, but at least you didn't format it (though it seems you were close to that point). Once it's damaged, it's damaged, and doing anything else with unexpected data (FAT on an NTFS partition) in the boot sector will cause further damage.

If you're really lucky, you'll have an NTFS partition with only slightly lost data, and Windows will boot fine.
If you're lucky, you will have an NTFS partition with only slightly lost data.
If you're not as lucky, you may have to try harder to recover your data.

Second: let us know how it goes

P.S. You may have also run fixmbr to try and fix your MBR. Testdisk can also help you recover from this.

 

[Nothinman]

and of course, it overwrote my Master boot record with a FAT32 file system

That phrase makes no sense at all the MBR is completely separate from the filesystem used on any of the partitions on a drive.

 

[Maluno]

Thank you very much for such an informative post, xtknight, I really appreciate the help. I'll be trying what you've recommended tonight.

By the way, I had mixed up the the boot sector and mbr, so thanks for the clarification. This forum works because of helpful people like you.

 

[Maluno]

Just to provide an update on my situation, I downloaded a linux rescue live cd which had the test disk tool on it, like xtknight suggested. I ran the tool, and did the following to the 238GiB {HPFS - NTFS} partition that was detected on my main HDD, (the 250 GB Seagate drive which I had previously installed windows on):

Rebuild BS >>> I used this tool, which listed the boot sector status as "bad," yet the backup boot sector as "OK." It fixed my boot sector, so that both sectors are identical, and the status now says, "Extrapolated boot sector and current boot sector are identical."

Repair MFT >>> I ran this one once and repaired the master file table using the "MFT mirror," (I guess that's just another backup). The status now says "MFT and MFT mirror matches perfectly."

MBR Code (Write TestDisk MBR code to the first sector) >>> I ran this utility to rewrite the MBR.

After doing these things, I tried to boot into windows directly, but was still unable to do so, (I just get random blinking characters and colored boxes flashing on the screen). BTW, when I try to use the analyse feature in testdisk, it detects the disk geometry/partitions as OK. I've tried booting to the mbr and to the first partition on the HDD using the grub bootloader that was from the recue live cd.

Lastly, I used the windows xp pro recovery console to rewrite the mbr one last time, (it detected an invalid signature), yet I am still unable to boot into windows. I would still like to fix windows to be bootable, however, if that is not possible, I can at least use a live cd now to copy all of my data from the drive.

Any suggestions?

 

[Nothinman]

It's likely that all or some of the data is corrupt on that disk, random blinking characters and colored boxes suggests that it tried to execute random gibberish. If there's no critical data on there just format the thing and move on.