[topgear]

There's no special raid hdds. You need to setup it through bios.

If you setup raid0 with your existing 1Tb & a new 500Gb you will get only 1TB disk space
after setting up the raid0.

For raid0 ( which gives maximum performance ) you need to have 2 same capacity ( & indentical like the cache same amount ) HDds & it would be more better if the drives are from same model & manufacturer.

As raid0 wants two same capacity HDDs. After setting up raid0 & using it you will feel the real performance gain. But the chance of data loss is also great if something goes wrong with the hdds.

I would recommend you to buy 2x seagate 7200.12 500GB drive to setup raid0 & use the existing 1TB as backup drive.

Do note that after setting up raid0 all of data will be lost. So back it up 1st.

You need to setup Raid0 array 1st through bios setup.. Then you have to install the OS.
Do note that while installing XP or even vista the OS may ask you for storage controller drivers. You need to integrate those drivers in xp install CD using nlite or incase of vista just copy them to your pen drive & load the drivers when installing windows. Otherwise the os may not be able to see your RAID0 setup.

For more information consult your mobos manual or online manual. There are a huge number of guides regarding raid. Do look at them.