RAID 0 is where you have two hard drives set up like they are one. This is done during the Windows installation and depends on the motherboard exactly how it's set up. What essentially happens is 1/2 the data is written to each drive...since each drive is only responsible for writing/reading 1/2 the data it is faster. The downside...if one drive dies, you
lose all the data.
If you ask me personally, it's a lot of work and worry for very little performance gain. But, if you decide to do it, get 2 identical drives...say two 500gb ones. The total volume of the drives you RAID will be double. So, two 500gb in RAID 0 will give you a full 1tb of storage...but remember the risks associated. I used to run raid all the time...it is faster than a single drive, but
any SSD will be way faster.
If I was giving you advice (again, this is my opinion) I would scratch the RAID for now. Get you a nice single drive and be happy...save some cash and get an SSD down the road.
Remember, HD speed will make almost no difference in anything you do. Games play the same, music plays the same...only thing cool about SSDs or RAID is that Windows loads faster and games load faster....they don't play any faster...just load faster.