FAT32 USB drive unreadable after mounting on old Windows computer

How to use TestDisk to recover lost partition
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paolocesari
Posts: 1
Joined: 03 Dec 2021, 16:41

FAT32 USB drive unreadable after mounting on old Windows computer

#1 Post by paolocesari »

Hello everyone,
I have a 32GB USB drive formatted FAT32 usually used on Mac OS.
Yesterday I putted it on old Windows computer to copy a file ad the operation was aborted.
Now the USB drive isn't readable and I always see the terrible message "format drive?" (NO!)
I also tried to create an image backup with "dd", but it seems does't work.
Does anyone have any suggestions? How can I rescue the disk and the datas inside?
Thanks a lot!

This is TestDisk 7.1 log and the main problems are:
  • Partition sector doesn't have the endmark 0xAA55
  • The harddisk (31 GB / 29 GiB) seems too small! (< 31 GB / 29 GiB)
  • Partition can't be recovered

Code: Select all

Partition table type defaults to Intel
Disk /dev/sdc - 31 GB / 29 GiB - VendorCo ProductCode
Partition table type: Intel

Analyse Disk /dev/sdc - 31 GB / 29 GiB - CHS 30000 64 32
Current partition structure:

Partition sector doesn't have the endmark 0xAA55

search_part()
Disk /dev/sdc - 31 GB / 29 GiB - CHS 30000 64 32
FAT32 at 4/1/1
FAT1 : 2784-17775
FAT2 : 17776-32767
start_rootdir : 32768 root cluster : 2
Data : 32768-61439935
sectors : 61439937
cluster_size : 32
no_of_cluster : 1918974 (2 - 1918975)
fat_length 14992 calculated 14992
FAT differs, FAT sectors=0-16/14992
set_FAT_info: name from BS used

FAT32 at 4/1/1
FAT: cluster=2(0x2), pos=40992
...
FAT: cluster=7(0x7), pos=41152
file_pread(6,32,buffer,41152(20/6/1)) read err: Partial read
FAT: cluster=8(0x8), pos=41184
...
FAT: cluster=20(0x14), pos=41568
file_pread(6,32,buffer,41568(20/19/1)) read err: Partial read
FAT: cluster=21(0x15), pos=41600
...
FAT: cluster=42(0x2a), pos=42272
file_pread(6,32,buffer,42272(20/41/1)) read err: Partial read
FAT: cluster=43(0x2b), pos=42304
...
FAT: cluster=48(0x30), pos=42464
file_pread(6,32,buffer,42464(20/47/1)) read err: Input/output error
file_pread(6,1,buffer,42464(20/47/1)) read err: Input/output error
FAT: Can't read directory cluster.
     FAT32 LBA                4   1  1 30003  63  1   61439937 [DISK_IMG]
     FAT32, blocksize=16384, 31 GB / 29 GiB
This partition ends after the disk limits. (start=8224, size=61439937, end=61448160, disk end=61440000)
file_pread(6,16,buffer,10272(5/1/1)) read err: Input/output error
file_pread(6,1,buffer,10272(5/1/1)) read err: Input/output error
file_pread(6,16,buffer,10256(5/0/17)) read err: Input/output error
...
Disk /dev/sdc - 31 GB / 29 GiB - CHS 30000 64 32
Check the harddisk size: HD jumper settings, BIOS detection...
The harddisk (31 GB / 29 GiB) seems too small! (< 31 GB / 29 GiB)
The following partition can't be recovered:
     FAT32 LBA                4   1  1 30003  63  1   61439937 [DISK_IMG]
     FAT32, blocksize=16384, 31 GB / 29 GiB
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recuperation
Posts: 2729
Joined: 04 Jan 2019, 09:48
Location: Hannover, Deutschland (Germany, Allemagne)

Re: FAT32 USB drive unreadable after mounting on old Windows computer

#2 Post by recuperation »

Do not use dd as it is not suitable for potentially broken storage.
Use ddrescue as described in the manual.
Use a logfile, ddrescue calls it "mapfile", post it here, make a screenshot of the ddrescue command line overview screen.
If ddrescue fails contact a professional recovery service.
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