Win 10 to 7 rollback... what is going on with disk space?!?!

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k@rt

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Apr 17, 2012
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So after a buggy, unstable, crash-filled upgrade to Windows 10, I decided to roll back my system to Windows 7 Pro which I was running before.

The thing is, before I upgraded to Windows 10 I had 31-32Gb of space free on my C:/ drive.

I upgraded and then rolled back and after all that I had 31-32Gb of space free on my C:/ drive... so exactly the same space as before HOWEVER...

I now also have a hidden folder $WINDOWS~BT on my C:/ drive that wasn't there before! Now as I understand it the $WINDOWS~BT folder is erroneous update/rollback data that is no longer required to run the OS, and it can either be deleted or removed with Disk Cleanup

In my case $WINDOWS~BT is almost 5Gb in size, and if this data isn't required to run my system that means that the process of upgrading and rolling back has somehow freed up (shrunk my windows installation) by almost 5Gb. Is that normal?!?!

The only thing I can think of is that maybe this is something to do with the Winsxs folder. I did notice that in Win 10 for the first time it differentiated between the normally counted size of the folder and the actual size on the disk, but I don't really see how this is carried back to window 7.

5Gb is a lot of data and before I remove $WINDOWS~BT I would like to be sure about what is going on here.

Can anyone shed some light on this issue, pls?

Thanks!
 
Solution
wpgwpg
If you look in that $Windows.~BT folder, you'll see a sub-folder called Sources. Inside that folder is a file called Install.ESD that's usually 2.5 to 3 GB. That's the compressed version of the .ISO file used to install Windows 10. I don't know about deleting the $Windows.~BT folder, but I do know that you can delete the Install.ESD file and free up 2.5 to 3 GB because I've done it on several occasions. My guess is that you could delete the whole $Windows.~BT folder, but can't speak from experience. If you have another way to boot that PC (e.g. a Linux disc), you could try renaming $Windows.~BT then rebooting and see if that works normally.
I suspect that Shaun o is right when he says you had the folder before upgrading. I...
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wkwilley2

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Once you "reserved" your copy of Windows 10, Microsoft started downloading prerequisite files to facilitate the installation.

That folder is also where the Windows 10 files go before you initialize the installation, so those files were already there before you gave your computer permission to install Windows 10.
 
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k@rt

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If they WERE there then they certainly were NOT in a hidden folder called $WINDOWS~BT... I know for a fact that folder was not on my system before I did the upgrade. Also when I actually did the upgrade itself the first thing that had to be done was for the Upgrade assistant to download 2-3Gb worth of installation files (I think about 2.5Gb)

When I said I wanted to upgrade I had, 31-32Gb free... then I downloaded the 2-3Gb install file which took me to 28-29Gb space free, but at that point still running Windows 7. Then I did the upgrade itself which took me to something like 21-23Gb free space, plus folders called $WINDOWS~BT and windows.old.

Now I cannot say 100% for sure that I didn't have 5Gb of other Windows 10 installation files somewhere else that I didn't know about... but I am sure that the ONLY place they could have possibly been stored was somewhere in my Windows 7 C:/Windows folder. And if they WEREN'T stored there, they weren't on my machine.
 
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Shaun o

Shaun o

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We will start with windows 7 when you install it.

First of all if you have a hard disk that you have formatted before you install windows for example it has one partition.
When you install windows it creates a system partition.

It creates the partition for when it reads files off the supplied install dvd, to uncompress installation files as an example.

When you upgrade to windows 10 it needs to do two things, create the backup of windows 7 for rolling back from 10 to 7.
But it also needs to create the same, or a new system partition where it can uncompress installation files for windows 10 setup.

So you end up with. the windows.old file for reverting back to windows 7.
And when you do.
You have the folder or system partition, used by windows 10 for the uncompressed installation files still left.
The 2.5GB size would or should of been the compressed installation and the 5gb windows folder is where the files were uncompressed unpacked it will reach 5gb in size.

If windows 10 for example was put on a single layer dvd disk 5Gb would be too large to put on the disk as it has a maximum of 4.7Gb of storage.

So the files like windows 7 provided on a dvd are compressed down to a size that will fit on a single sided dvd medium.

And uncompressed when installation starts to a temporary folder.

As an example with windows 7 just right click on the windows folder on it`s own, and properties. You will see uncompressed just how big windows is as the complete installation of uncompressed files.



 
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K

k@rt

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Thank you very much for the detailed explanation. As I understand it what you are saying is that my 5Gb $WINDOWS~BT folder is the uncompressed installation files for Windows 10 that the compressed 2.5Gb download was extracted to.

This makes sense to me, what I am not so sure about is why however my Windows 7 installation is now 5Gb smaller (approx) than it was before I upgraded. Or are you saying that all the time I was using windows 7 somewhere on my hard drive was a "partition" where uncompressed Win 7 install files were located, and that they were removed when I upgraded to Windows 10 and "replaced with" (but not in the same location) the uncompressed Windows 10 files... which I am now seeing and counting as 5Gb of "extra" data I didn't have before? That's the only way I can use what you are saying to explain the 5 extra Gigabytes of space I seem to have recovered.

But actually, the thing I really want to know is can I now remove $WINDOWS~BT completely from my machine without incurring any adverse effects?
 
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wpgwpg

wpgwpg

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If you look in that $Windows.~BT folder, you'll see a sub-folder called Sources. Inside that folder is a file called Install.ESD that's usually 2.5 to 3 GB. That's the compressed version of the .ISO file used to install Windows 10. I don't know about deleting the $Windows.~BT folder, but I do know that you can delete the Install.ESD file and free up 2.5 to 3 GB because I've done it on several occasions. My guess is that you could delete the whole $Windows.~BT folder, but can't speak from experience. If you have another way to boot that PC (e.g. a Linux disc), you could try renaming $Windows.~BT then rebooting and see if that works normally.
I suspect that Shaun o is right when he says you had the folder before upgrading. I suspect it was there and you just didn't notice it because MS downloads it to Windows 7 systems with Windows Update whether you ask it to or not. Sneaky devils, those folks at MS!

Good luck.
 
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