First off, did you make sure you entered your BIOS setup utility and auto detected the hard drive?
You said your BIOS beep code is reflecting a video card issue, are you able to see anything on the video screen?
Sometimes beep codes can be misread, the error could be a RAM module error, perhaps a module may have became loose.
I am sure it has to do with the fact that you recently disturbed something while you were adding the hard drive.
Also, anytime you are doing any work inside the computer case, you have to exercise caution.
Always ground yourself first to the computer case, before you touch any components inside the computer case. Static electricity from your body can destroy sensitive components found inside the computer case.
Edited by MrBruce1959, 30 July 2010 - 02:34 PM.