I built my PC with a 128GB ssd as a boot drive and I obviously need more space. I have some old HDD's laying around the house and was wondering how I would go about adding them in. My concern is that because they have things on them (old OS's) it'll mess up my current config. Is there a way to plug in a hard drive reformat it to erase the OS and the data inside, and use it as storage? Thanks in advance for any advice.
You don't have to reformat the HD to use it in your new computer. Just make sure the boot order in your BIOS is set to boot from the SSD before the hard disk, and it doesn't matter what is on the disk (It will always boot from the SSD first then).
And you can reformat the disk to use in Windows. Right Click the drive and select "Format" when you are booted from Windows.