I remember seeing this when Win7 first came out. In fact, I used it once to help a friend. But I lost it

.
There's a way to install a
lower version of Windows from an Ultimate CD. Actually, the tip worked both ways. Basic premise was to copy the CD files to a hard drive, modify one (1) particular file, then create an ISO on a new CD and run the install. Of course, the proper key is required for the version you are installing.
My sailing friend headed out to see his SO this evening. He took along my Ultimate CDs, 32-bit and 64-bit. His lady's laptop locked up on her, and he couldn't cure it over the phone (she's somewhat less than technically patient

). He created a recovery disc when they bought her laptop, but may not be able to find it. And those recovery discs don't always work as advertised - I've had two (2) that failed, and have heard of others. So I loaned him the CDs I bought, with the understanding that he'd use the key on her laptop.
But I think he'll need to do the correction thing in order for them to work. I've mentioned before that my short-term memory - say five (5) to ten (10) years - ain't what it used to be, and it's failing me now in finding the aforementioned instruction

.
So the question is, does anyone have a link to that instruction, or perhaps know how to accomplish the kinda/sorta downgrade?