I tried transferring a backup folder from an XP laptop to a 7 laptop via USB, and 7 pitched a royal hissy fit. It wasn't TWRP, it was the other backup app. (too damn early in the AM to remember)
It has to be something in 7. I buy from a PC repair shop, and I get the bare bones OS.
No security, nothing added. The owner knows me and knows that installing what I use for security is the first thing I do. I turned off security and 7 was still having fits.
I turned off all communications with MS itself as far as I know.
I had the tech upgrade to 7 pro just to get virtual XP. and I asked about using that to back up. I use it for Adobe Illustrator 8, and XP yells about no security each time I open in, but it's running inside 7. The answer was more about using it to code rather than back up, so I'd like to know, too. I still have the XP laptop, and I can still use that if I have to.
I do have most of the files from the transferred backup, but I don't trust them. I don't like the fact that besides backup, 7 won't let me copy over the whole phone. I could copy it without a backup program and did that on XP just to keep one set of data current.