The drive is certainly adequate for your needs.
The real question is if it's necessary to have a third drive just for data. Some people swear by it. I'm a firm believer that Premiere Elements is a consumer program and it should run fine on a well-tuned, off-the-shelf computer. It always has for me.
In my books, I list my "real world" minimum specs for a video editing computer. For standard-def video, a dual-core processor with 4 gigs of RAM and a big hard drive is more than adequate. For AVCHD video, I recommend a quad cord oe i7 processor. For most efficiency, a second hard drive is a great add-on.
But you really shouldn't have to do all this Black Viper rigging just to edit video. Personally, I wouldn't sweat all these modifications. Just keep your computer tuned, per the FAQs to the right of this forum, and match your project specs to your source video and you should get excellent performance with your new machine.
The I/O setup for video editing is a point of debate. The performance gains possible can be very large, when going from a single HDD to a 2x setup, but less so, when adding a 3x setup.
There are some choices to make, and they can depend on exactly what one wants, or needs.
One thought is that fully splitting the I/O load will improve the total performance, but at the cost of "housekeeping" down the line. From a pure performance standpoint, having the OS and progrms on the system HDD, then the media on another, and the Projects and their Scratch Disks on a third, will give one a gain. The location of the Page Fiile should also be tested. It is often placed on the system HDD, but some improvement might be gained by having it located elsewhere. This will depend on one's system, and only testing will indicated whether the improvement can even be charted. A more important aspect of the Page File (Windows Virtual Memory) is probably whether it is dynamically, or statically managed. This ARTICLE addresses those choices. On my laptop, I found that placing my Page File (statically managed) on my E:\ drive made a slight improvement in performance.
Now, regarding Scratch Disks, for pure performance, there is something to be said for splittling the I/O load there, BUT, then one no longer has everything in the Project in one place, so housekeeping is a bit more complicated. I give up that performance gain, to keep things together, and like keeping my Scratch Disks within the folder structure of my Projects on the same HDD.
For some general thoughts on the I/O setup, this ARTICLE will be useful. Note: it talks about "ultimate" performance, and some of the gains may well be minimal.
Though I have many multiple, separate HDD's (3x on the laptop and 8x on the workstation), I agree with Steve, that a 2x is adequate for most video editing. If I had a good 2x setup, and access to more HDD's (your additional should work fine), I would go with 3x, but not expect to see any dramatic improvement in performance.
I was under the impression that the Scratch disks where sort of a temp file. They where for rendering that work area. So, house keeping is not as much of an issue. You probably only need to have the scratch files for the projects you are activley working on. Just curious.
I'm only considering the third drive because I like to tinker. My new system will have it's own bottlenecks. We'll see how it behaves when I fire it up. I'm considering making the jump from Elements to Pro. But, I really need to justify that move somehow.
Well, so that there is no confusion, the Scratch Disks for PrE are different, than those for PS/PSE, which are very "temp" files, used to create "virtual memory" to augment RAM. In PrE (and PrPro), they are also sort of temp files, in that they are created for various aspects of the editing. They are basically "working files," in that respect. They are Render files, CFA (Conforming) and PEK (Waveform Display), and such. When authoring a DVD/BD, they are also used. These can be regenerated, if necessary (the CFA's, the PEK's and a few others ARE necessary), either automatically upon Opening a Project, or by hitting Enter to re-Render the Timeline, or part of it. The "housekeeping" is when it comes to clean up after a Project has been completed. If the Scratch Disks are located Same As Project, then it's simple. If elsewhere, one must manually find them, and Delete them from that other location. With Same As Project, one just Deletes the Project's root folder, Deleting all sub-folders in one click.
Hope that helps, and good luck,