Windows repair doesn't detect unbootable Windows as installed

[SIW2]

You could try copying acpi.sys from another machine. Sounds like you have more probelms than just that.

Or you could do an install from win7 installation media, but don't format the drive. Your old installation should then be saved into a folder called Windows.old ( if there is enough space on the drive.)

You can borrow my bootable repair media. ( for repairs, it is not installtion media)