Replacing PSU- HDD Failure

[demope]

I was replacing my PSU today (Corsair Tx750v2 from a Corsair TX850W due to a series of shut-downs). Power up the system, HDD is not found. I switch back PSUs, try different Sata cables and ports on my Mobo, and still my HDD is not found. I find an old HDD from a 2008 Sams Club HP, and I was able to boot up.

What could've happened to mess up my HDD? My main problem is that I need the data on this HDD. It has a good portion of unbacked up music on it (hadn't backed up since April) and most importantly, my 64 bit Windows 7. The problem is that this is the student version of Windows 7 and Microsoft Office 2010, and both keys were accessible through my college. I am now graduated and preparing to enter medical school, so I no longer have access to these perks.

What did I do when I switched PSUs?


System Specs- built August 2010-

HDD: WD Caviar Blue 500gb
Mobo: Gigabyte X58A-UD3R Mobo (http://www.newegg.com/Product/Product.aspx?Item=N82E16813128423&Tpk=x58a-ud3r)
CPU: i7-930 (http://www.newegg.com/Product/Product.aspx?Item=N82E16819115225&cm_re=i7_930-_-19-115-225-_-Product)
PSU: Corsair TX850 (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139009&cm_re=corsair_tx850-_-17-139-009-_-Product), now Corsair TX750 v2 while I RMA a new one
Graphics Card: PNY Geforce GTX 470 (http://www.newegg.com/Product/Product.aspx?Item=N82E16814133341&Tpk=pny+geforce+gtx+470)
RAM: Muskin Redline 6 GB-3x2 (http://www.newegg.com/Product/Product.aspx?Item=N82E16820226121&cm_re=20-226-121-_-20-226-121-_-Product)

 

[mosox]

Can you see it in the BIOS? Can you see it in the Device Manager?

 

[kajabla]

If the old PSU was broken, it could have been causing electrical problems that could, possibly, have broken that HDD. Try it in a different computer.