Adding existing sata drive as 2nd without losing data...not recognized

Sounds like it was not just Windows that got hosed, it was the hard drive itself. I gather Dell has had your disk and done some work on it, but you believe they did not damage its contents, and they say the hardware side of it is OK. So you will need some software tools to gain access to its data, since the new windows installation on another drive cannot see it.

One tool that has worked for many around here is called GetDataBack NTFS. It is not free - you have to buy it. BUT they offer a free trial version kind of deal. You can download and run it for free, and it will show you exactly what it can find and restore for you. If that looks like all you need and you like the price, you pay and it finishes the recovery job. If you don't pay it does not recover, but you know what IS on your disk to be recovered in some other way.