I have read the sticky's but it did not help my problem so here goes.

okay, so i will start from the beginning. I have a fairly old computer and I bought a graphics card for it (ati hd4730 to be exact). I did not know that this video card needs to be connected to a 6pin PCI-E, so i bought a molex 4pin to 6pin adapter. there's 1 6pin end and 2 4pin ends.

I plugged both the 4pins and turned on my machine but nothing appeared but a black screen (i knew it was connected because it did not say no signal) and my hard drive did not sound like it was spinning. I forgot to mention that i have a 500W PSU. When i unplug the 4 pins from the adapter, my hard drive would start up and if i was lucky and reconnected it, my windows would start with the monitor connected to the graphics card but it would freeze and if i restarted the computer it would restart then go back to the black screen.

I was messing around with the power cables while the computer was still on and i think i short circuited my hard drive because my windows would not start up anymore even with the Onboard Graphics connected to my monitor, please help me. I have 2 problems but right now i want to know if i can fix my hard drive cuz i had some important things in it. thanks.

Firstly, if your data is important, you should always have a backup of it. Too many people wait until they have a problem before thinking about their data. What if your hard drive is completely dead?!?

Secondly, you need to check that the data and power cables to it are firmly fitted then check that it shows up in your bios.

and thirdly ,never plug any thing in when computer is powered on ,if you plugged the video card in after you turned on the power, you may have damaged the video card.

what is make and model of the computer ,or if it a custom build ,what is make and model of the mothereboard

..do you said that it was a old model when you add a hardware remember it affects a power supply of the motherboard...just aware of that...and your hard drive just try to any computer...when it is ok...your unit is a problem..but if its not your hard drive has a bad sector..it affects your os to run normally...