Adding an old hdd on a new computer

[Robert_288]

I want to add a second hdd to my computer, but since i salvaged it from another pc (which doesnt work) it still has windows on it. Will this cause problems? if so how do i proceed?

 

[RealBeast]

Attach the old drive with the computer off, then after startup remove any data that is not yet backed up, then do a quick format on it.