(1) Western Digital 500GB WD5000BPVT, 5400RPM, 8MB Cache for $43.44 + free shipping (with amazon prime) at amazon. This works out to $0.08688/GB
Click here to purchase.
This drive is the Advanced Format technology increases media format efficiency. This is better for newer machines (Windows XP requires a software from Western Digital)
I have been searching for hard drives ALL morning, and I made a nifty little spreadsheet of Price per GB, and this is one of the best deals out there, with large capacity. click here
(2) Next best deal is Western Digital Scropio Blue WD6400BEVT SATA drive 640GB, 2.5" 5400RPM, 8MB Cache, with 3 year warranty for $49.00 + tax + shipping at Western Digital Loyalty Program. Click here.
You will need a old western digital hard drive serial number for this to work. You need the serial number to put in to get the deal. This will void the old drive warranty.
For me, in Virginia, total was $58.45. This works out to $0.091328/GB
I did not do 1TB drives, because these drives are 12.5mm thick versus the standard 9.5mm thick, so they can not work in my laptop. Some newer laptops might have space for the new thicker drives. The 1TB drives have 3 platters, versus 2 platters of the standard drives.
If you look on the spreadsheet, you can see where to buy the cheapest 750GB drives as well. It has a lot of information, so if you are looking for a drive, this should guide you on everything you need to know.
POWERED eSATA External Hard Drive Enclosure
I am using this hard drive with a "powered eSATA" port on my laptop, so that I can do my Lightroom editing from this hard drive. I did a lot of research before finalizing on this enclosure. 2.5" USB 2.0/eSATA Aluminum External SATA HDD Enclosure (Black) Power over eSATA!. This allows me to plug in the hard drive without needing external power. My laptop has a combo USB/eSATA port. Normal eSATA does not supply power to the hard drive, so you would need external power. I wanted portability, so I did not want to have to supply external power to the portable external hard drive. You would NEED to verify that you have a combo eSATA+usb port, or else this will not work. I am really happy with this solution. Now, I wait for delivery of these