So I recently did a fresh install of Windows 7 Ultimate 64-bit on a new HDD. Everything worked out fine and I was able to transfer over my documents and such perfectly over from my old HDD (with W7 Home 32-bit) to my new HDD (with W7 Ult 64-bit). I was tired of having to choose a which HDD to boot from every time I started my computer so I tried to just format my old HDD since I've already taken everything I needed off of it.
Disk Management wouldn't let me format it so I tried to change the label from C: to A: seeing if that would change anything; then changing my new HDD from E: to C:. It wouldn't let me do that so I restarted my computer and BOOTMGR is missing pops up. I go into my BIOS and figured I had to boot from my old HDD to get an option to load my new HDD's OS. After looking closer I think the problem is that my old HDD has the "System" property on it while my new HDD doesn't.
I guess my question is: what's the proper way to format an old HDD so I can only boot from a new HDD with a fresh installation?
TL;DR: Installed new OS on new HDD. Want to boot from only new HDD, format old HDD and use it for storage only. How to do properly?
NOTE: Please consider that I would not like to do another fresh installation as I've already downloaded and installed programs and such. I'm on a really low speed internet connection so I would like to avoid that at any costs.