In my hugely popular article about Transferring Windows 7 OEM license to a new hard drive, I kept insisting, that you absolutely positively need to know your SLP-key before processing. Couple days ago I was working on a recovery of a failed hard drive and realized, that it's not completely true.
As the troubled drive had already been replaced with a brand new SSD, I had the HDD in an USB-dock for investigation purposes:
The new Windows 7 OEM had already been installed, but not activated. As I didn't know the SLP-key I was planning to do the phone activation with COA-key. At that point I realized, that it was possible to use the Magical Jelly Bean Keyfinder from another drive:
It wasn't much simpler than that! A simple copy/paste -operation to get the key in and Windows activated.
The requirement seems to be to point to a %windir% and system32\config\ is assumed on top of that.