I bought another computer and was trying to use my "old" hard drive and install it in the "new" computer. Whenever I boot up it will get to the windows symbol startup screen. Then it will black screen on me for a few seconds and then restart and will continue to do this unless I choose Startup Repair. But if I use the hard drive I recieved with the computer it will start up fine and my "old" hard drive will show up as secondary drive. Should I try reinstalling my whole OS and format both drives?
A re-install of Windows should correct any problems that you are having. Your problem is probably because the older hard drive's Windows installation lacks necessary drivers to work with your newer computer and a re-installation of Windows should resolve that problem completely.