No, you can't use external USB -- it's too slow.
At best, maybe an eSATA drive would work. But an internal drive is always the best option, be it IDE or SATA.
Adding a hard drive is more or less idiot-proof with modern computer cases. As long as there is room in the case (it's not some tiny slimline or micro case), then it should be obvious where a new drive goes. They've made computer building so easy that it's closer to kindergarten exercises (round peg in round hole, square peg in square hole) than the techie endeavor it once was. It's all plug and play now, no jumpers to mess with, etc. Checking email is harder to do. I have more trouble operating my stove.
These are the stores I generally suggest and use myself for good hard drive deals (in preference order):
Anything made by Seagate, Western Digital or Hitachi, in the 1TB range, tends to be fine. Assuming SATA, you're looking at spending $75 at most for an internal drive. I personally prefer Seagate drives, but will buy the Hitachi when on sale for substantial savings over the Seagate options. Western Digital drives don't tend to be in the same price range, and are no better quality-wise. If anything, WD drives can be noisier.
Here's a Seagate 1TB for $70 shipped: http://www.amazon.com/gp/product/B00...SIN=B00272NHOK
Here's a Seagate 1.5TB for $85 shipped: http://www.amazon.com/gp/product/B00...SIN=B00066IJPQ
Another $15 for another 500GB is worth it, in my book.
You'll need a SATA cable for $4: http://www.amazon.com/gp/product/B00...SIN=B0001Y8UI4
I don't really see any better deals at the other stores right now. And Amazon
is the best place to deal with anyway.
Internal hard drives use the power supply in the computer. External ones do not have that hookup option, and must have power supplies by dedicated electric plug. Some small drives leech power from the USB2 ports, but even that can be an issue. Not all computers supply adequate power through USB rails. I have problems with several systems here, when given USB-powered drives.
If you have one(s) linked where this site gets a cut of the money, so much the better.
Thank you very much for that.