This file came from another computer and might be blocked

"This file came from another computer and might be blocked to help protect
this computer." http://i.cubeupload.com/8NS7oY.jpg

I saw a JPEG file on my WinXP computer that I didn't recognize and I simply
right clicked its properties to find that message above.

Googling, I find that message can be disabled.
https://social.technet.microsoft.com...ovistasecurity

And that it's not specific to JPEG files:
https://answers.microsoft.com/en-us/...8-8c91e5d436bf

But that leaves three basic questions:

1. How do you un-set this block property en masse, for all JPEG files?
2. If desired, how is the block property set on the JPEG in the 1st place?
3. Where exactly in the JPEG file is this block property stored?

Niamh Bodkin wrote:
"This file came from another computer and might be blocked to help protect
this computer." http://i.cubeupload.com/8NS7oY.jpg

I saw a JPEG file on my WinXP computer that I didn't recognize and I simply
right clicked its properties to find that message above.

Googling, I find that message can be disabled.
https://social.technet.microsoft.com...ovistasecurity

And that it's not specific to JPEG files:
https://answers.microsoft.com/en-us/...8-8c91e5d436bf

But that leaves three basic questions:

1. How do you un-set this block property en masse, for all JPEG files?
2. If desired, how is the block property set on the JPEG in the 1st place?
3. Where exactly in the JPEG file is this block property stored?

The blocking information is stored as an Alternate Stream.
And Alternate streams are an NTFS feature.

https://blogs.technet.microsoft.com/...reams-in-ntfs/

Here is a basic tool for Streams.

https://technet.microsoft.com/en-us/...ernals/streams

Paul