How to add an extra HDD that already has windows?

I found one of my old HDDs and i wanted to boot it up on my pc as a secondary HDD so i can have a look whats on there and stuff, i tried it on its own and it worked but my mouse and keyboard wouldnt work so i couldnt get onto it.

How can i add it so it runs as a secondary so i can access the files but still use my current HDD to use windows and everything like that.

Thanks

connect the main HDD that loads windows, make sure in the bios that this HDD is the boot drive.

connect the second HDD and you should be able to access it through windows once its booted.

Hey there, marrissey.

I second ED209's suggestion. Just go ahead and connect both drives, but use your current OS drive as the first booting option, instead of the old one. It was pretty lucky that you were even able to boot to Windows with the old HDD. By the way you might have legacy USB support settings in your BIOS, which could help with the mouse and keyboard issue.
Note that sometimes when you try to access an OS drive with a different Windows installation you might need to take ownership of that HDD/SSD in order to be able to get to your data. I don't know what's your version of Windows so I can't post a tutorial, but it should be easy enough to find by googling it.

Cheers!
Boogieman_WD