You may get different responses to this question, but as far as I know, you can't restore an old installation of Windows from the Windows.old folder. Theoretically though, I guess it may
be possible using a linux boot disc and deleting the Windows folder and then renaming the Windows.old folder to Windows, however, I would seriously advise against this as I've never tried something like this. Looks like a good project for a Virtual Machine
To move on though, are you finding that there are certain setups or programs that you had on the old Windows installation that you're missing on the new installation? Why exactly are you wanting to restore the old?
Edit: Concerning restoring the old Windows setup... it's plausible that doing exactly what I outlined above may
fix the issue, but again, that all depends on what exactly the issue was. If it was not booting, then the reinstallation may have fixed the boot sector or MBR that was corrupt. If something in Windows was corrupt though, then restoring the old would just reproduce the same issue you were facing originally.
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?