Please help with adding a HDD

[mwagen]

I've run out of storage on my 250gb nvme and I have an older but perfectly good working 1TB HDD that I want to add for more storage. Configuring multiple storage devices is an area I know nothing about (always just ran one drive), but what makes this situation even more confusing for me is that my old HDD already has another version of Windows installed on it (I want to say 7 but it could even be Vista..) along with some old personal files that I want to keep. I know there's at least 500gb of free space on it, probably closer to 750gb, and if it does in fact have Windows 7 on it then I believe the Windows 10 I'm currently running is descended from this old drive. So, I guess I don't know how that's going to work if I just add this new drive in if it's already got Windows on it. If this is a simple thing somebody could help me with or point me toward some good walk-thrus I'd appreciate it, thanks.

[Electronics Wizardy]

Just plug the drive in. The system should boot windows 10 and the old os won't be used. You can then copy files from the drive. 

[DarkEnergy]

If the above response doesn't work, make sure your 250gb nvme drive is set as the primary boot drive in your bios. Otherwise you shouldn't have any issue using this drive. I'd just toss all of the folders on it into one folder and label it "old" or something like that. Then use it for storage.