The HDD crashing can be traced to one of two things.
1. The Molex power connector is bad. Try replacing.
2. The SATA data cable is bad OR the SATA connector on the motherboard is bad. Try a new SATA data cable. Try a different SATA connector on the motherboard.
If no other SATA connectors are available on the motherboard, then consider replacing both HDDs with a much larger capacity (750GBs?) and connect the new HDD to the known good SATA connector. You can use the old HDDs as external drives.
For transferring the OS to the new drive a good option is Apricorn's drivewire cloning device. http://www.apricorn.com/product_detail.php?type=family&id=39
This is what I did when my laptop 40GB HDD started to "click" indicating impending failure. Replaced the HDD with a 320 GB HDD. In your case, HDD failure is not the problem.
Something t consider.