All of this is determined by your budget.
What's your budget?
How much are you willing to spend and what do you want to achieve?
I would do a mirror RAID for data redundancy. Many motherboards have this built-in.
If you are low-budget and want to keep as much of your old system as possible, the #1 component to think about is the Power Supply, as a bad power supply will kill-off the motherboard, hard drive, video card, CPU and/or all of the above, as well as itself when it goes.

SSD's are great for start-up speed, if you have a lot of crap running. I agree with the previous poster that for most people they are an expensive and inferior luxury. You spent $300 and your computer starts 45 seconds faster. Woo. Hoo.


However a RAID 1 (mirror) is 2 HD's and ensures that if one (cheap) HD fails the data is still good on the other.

Here's a nice 500 Gbyte WD Black for $67:
http://www.newegg.com/Product/Produc...82E16822236345

You can get two of these in a RAID 1 for less than $150.00. I'd discount any advice that is based on the idea that any hard drive is "reliable" or "more reliable" than others. ALL HD's are prone to failure. They might last 5 years, they might fail after 5 days. I DON'T think that any current hard drives are going to last 10 years.

Also, MS support for XP has ended. It seems like your needs are fairly low-end. I just guided a couple of customers to buy a nice quad-core desktop at Wal-Mart for less than $400. If you don't need top-shelf, don't be too proud to buy a cheap desktop at Wal-Mart.