Copy data files from an old hard drive to a new system
Question: My dell 8400 tower went down, replaced power supply and ..nothing. How can I get everything off the hard drive, install into another tower, or take it somewhere to download to external drive?
Answer: From what you've described, it sounds like your motherboard is probably fried. Since the Dell 8400 series run an old Pentium 4 processor, it's probably not worth bothering with trying to replace the motherboard and you're better off trying to get the data off the hard drive and replace the system altogether.
You have a couple options for doing this. You can hook up the hard drive as a slave drive in your new system, or you can use an IDE adapter that plugs into a USB port and treats your hard drive like an external USB drive.
Either way you'll need to remove the hard drive from your old system, which is easy to do. Remove the screws from the outer casing (some cases let you slide the side off without removing screws) and locate the hard drive. There will be a flat thin cable about 2 inches wide connecting it to the motherboard. Remove the screws holding the hard drive to your case (usually 2 on each side) and then remove all cables and power cords going into the hard drive.
The easiest way to get data from your old hard drive onto another desktop system or laptop is to connect it using an IDE adapter. The adapter will connect your hard drive with your other system's USB port, and will let you copy files over just like it was a USB flash drive.
The IDE adapter I have is the Sabrent DSC5 that I found for $25 at Fry's and is also available on Amazon for under $20. It works with regular 3.5-inch hard drives that are found in desktop systems, 2.5-inch drives found in laptops, and also works with both IDE and SATA drive types.
Once you connect the hard drive with the USB port on your other system, restart the other system and it will power up your hard drive and recognize it as an additional drive in Windows Explorer (or Finder on Macintosh systems). You'll be able to drag files and folder from the old hard drive to your new system.
You can also install your old hard drive into your new system as long as there is room in the desktop case for another hard drive, and as long as there's an available IDE or SATA connector on your motherboard.
Most newer systems use SATA (the small red cable shown in the adapter image above), but they should also have an IDE connector on the motherboard that you can plug your old drive into.
When you restart the system it should recognize it as an additional hard drive (D drive if no other drives or CD/DVD drives are installed) and you'll be able to copy files and folders over just like with the IDE adapater approach mentioned above.
For most people, the USB IDE adapter approach is a lot easier.