When you boot up with the System Repair Disk have you tried System Restore to see if your restore points could resolve.
It may be possible to copy the file from your other machine onto something like a Flash drive and then drop it into System32, but you would probably need to take ownership of it.
sevenforums has this facility which will add Take Ownership to your right click context menu.
https://www.sevenforums.com/tutorials/1911-take-ownership-shortcut.htmlRight click on the acpi.sys file then click on Take Ownership - you can then drag and drop it into the Flash drive.
You'll probably need to copy & paste it into the affected System32.
If you have a Win 7 install disk that includes SP1 then you can boot up with that and click on Repair your computer on the Install screen.
Select Command Prompt and enter -
bcdedit |find "osdevice"
Then using the partition letter instead of the X I've used, enter -
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
This may restore the missing acpi.sys file.
For clarity, that is a Pipe symbol before find which is the uppercase of \ and note the space before each /
If you are unsuccessful with your restore points or copying the file from your other machine and you don't have a Win 7 SP1 install disk, then I can burn and send you a couple but it will be after Boxing Day before I'll be able to send them to you, providing it isn't a higher version than Pro.
PM me with your address and version of Windows and 32 or 64 bit if you require them.
With a Win 7 SP1 install disk you can also restore a Win 7 registry to defaults but it can be a bit sluggish after.
I'm not sure if this will take the registry back to before SP1 but here are the cmds you would use after booting up with the install disk and using Command Prompt.
Once on the command prompt window, type c: and hit enter.
Type the following commands into the command prompt - each one of these statements copy the original registry files to the current registry directory.
copy C:\windows\system32\config\regback\system c:\windows\system32\config\system
copy C:\windows\system32\config\regback\software c:\windows\system32\config\software
copy C:\windows\system32\config\regback\security c:\windows\system32\config\security
copy C:\windows\system32\config\regback\sam c:\windows\system32\config\sam
copy C:\windows\system32\config\regback\default c:\windows\system32\config\default
Press the "Y" key after each copied file. This confirms that you want to overwrite the existing registry files.
Enter exit to close the cmd window and remove the Windows 7 installation disc from the drive and reboot the machine.
The registry will now be restored to its original settings.
You may want to create a system image before running these cmds.