Q) When I bought my computer six years ago, it had a then-enormous 8 GB hard drive, which arrived partitioned into four "separate" drives. I'm ready to buy a new computer and, since I plan to edit video, I want to buy the fastest, biggest everything, including a whopping 200 GB hard drive. Your articles suggest a second hard drive for storing video footage while editing.
Do I need a physically separate hard drive? Can the 200 GB drive be partitioned? The manufacturer of the computer I'm leaning toward offers a RAID 0 system that controls two hard drives (120 GBs each), so they work together as one 240 GB drive.
A) Not that long ago, operating systems weren't able to deal with large hard drives. They had to be partitioned so the file systems would work properly. Now, modern operating systems (Windows XP and Mac OS 9/OS X) have caught up and are fully capable of addressing larger hard drives. As far as partitioning is concerned, a partition doesn't give you the performance increase that a separate drive does. You asked about improved performance for video. A separate physical drive is a better option.
I still like to partition large hard drives for organization. I put the operating system on one partition, applications on another, utilities on another, and all of my documents on yet another. I also use partitioning as a precaution and possibly to save myself some trouble. If I lose a partition, I won't lose all the data on the drive. (Of course, if the drive fails, I'm out of luck.)
I also use partitions to help with building removable media. For example, I have partitions that are the size of a CD-R, DVD-R, a USB drive and a Zip disk. I let the operating system tell me when the drive is "full" and then I start burning the discs.