Windows 10 corrupts FAT partition checksum

I have a FAT16 partition (primary) that takes a total of 10.00MB of a standard USB drive. The rest of the space on the USB drive is unallocated so this is the only parttion I have there.

When I plug it in Windows 7 PC, regardless of whether I browse the files in that partition or not, the checksum of that partition remains unchanged.

However, when I plug the USB in Windows 10, the OS seems to write something to it and therefore the checksum is different, even if I do not open the "Removable disk" to see and browse (not alter) the files - the signature is different. It seems that Win 10 it writes or somehow changes the USB at the very moment it mounts/recognizes it.

What I have tried so far:

Changed the NoAutoMount reg key (located in \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\mountmgr) which did not work.
Marked the filesystem as readonly using diskpart -> that works, but is not a good solution as it is only applicable for the local PC. If I plug the USB in a different Windows 10 PC, then the checksum would be different (no readonly mode).

What could be the difference in Windows 7 (compared to Windows 10) that allows attaching and viewing USB content without altering any information on it?

Thank you in advance.

qntris

Posted 2017-09-11T13:20:10.407

Reputation: 11

2off topic as nota programming question. Better suited for SuperUser stackexchange. – scrappedcola – 2017-09-11T13:21:35.463

Please explain how changing = corrupting – I say Reinstate Monica – 2017-09-11T13:45:35.737

Fully clean the USB drive with diskpart. Then create a partition. – Biswapriyo – 2017-09-11T15:54:32.380

What I mean by changing is that by writing something on the USB (that I am trying to find out and eventually avoid), Win 10 actually alters the content of that USB (partition) and therefore the checksum is different. I have the image of this parttion (FAT16) and just upload it on an empty flash drive using any simple image upload tool. I need the checksum to be consistent - therefore I am wondering why Win7 does not alter the USB but Win 10 does. – qntris – 2017-09-11T18:52:36.473

Answers

Either your choice of filesystem is based on a too old filesystem for the wrong reasons or you are trying to use the USB stick for a very specific problem that could maybe be solved diferently.

I asume you mean the checksum of the whole fat16 partition is changed? when windows changes something, can you find what it does? write a folder, file or inside the filesystem table? Maybe if you change the format so windows would accept it and the target device, a different checksum doesnt matter.

according to your second point, you want to use it in multiple computers for a very specific purpose. ive read on multiple places, windows 10 changes the format: http://www.tomshardware.co.uk/forum/id-3328596/utility-access-fat16-w10.html#r19280266 could be that windows 10 changes your filesystem to Fat16 LBA ?

CodeAsm

Posted 2017-09-11T13:20:10.407

Reputation: 29

Thank you for that answer. Yes, by checksum I always mean the checksum of the whole partition. There is no visible change or file being added to the drive, but judging from the different checksum, the Win 10 OS probably adds something that alters the media. FAT 16 is mandatory in my case so filesystem remains as it is. I am eager to find out what is actually "different" in Windows 10, compared to Windows7 and whether we can tweak it. I am quite sure there is a solution to it - hope you guys can give me a hand with it. – qntris – 2017-09-12T04:39:47.680

You can try using HxD, a free very usefull hexeditor that can open diskdrives (start it with admin rights), default is read only, wich is fine. you can then read the whole drive and see whats going on. I would 1, use a PC that wont alter the partition, HxD read, maybe copy the whole partition or first 1 or 2 sectors and then the same on a win10 pc, compare the two and if the changes apear in a few bytes in the very first sector, its probably windows altering the Fat16 details a bit. copying under Linux can be done with DD, hexdump is a cli tool to view the contents in Hex. – CodeAsm – 2017-09-12T06:44:46.910