You'll probably get a variety of suggestions.  Mine is to read the specials in the Deals and Hardware section of the forum and consider getting some SSD drives.  Then it won't matter where you put the samples, it's all fast. SSDs are getting really affordable now and performance and location become a non issue.

Are you recording to the second drive? If so, then don't put your samples on it. In my experience it'll be a headache. Use the first drive for samples. Ideally, you want three drives. One for OS, programs, one for recording, and one for samples. Also, if using sample libraries, you'll want more than 4 gigs ram in your comp. Windows alone will use up 2.x gigs of ram just running. Hard to tell you what will work without more information.

If you want to use "older" Sample Players like TTS-1 you are fine. Otherwise your bottleneck will be the RAM. Processor speed will be a topic if you are planning to use newer plug-ins like Rapture Pro or Kontakt, because they hit the processor hard by calculations of filters etc. The Pentium Quad Core is a low energy consuming ATOM processor. It is a couple of times slower than actual CORE processors.
The hard drives are OK. A patient person can live without SSDs, so that is not a dealbreaker. Using the old Sample players the load times of sample sets will be tolerable.

OK, y'all.  Looks like I've got a little rearranging to do and will probably add more RAM.  Thanks to everybody for weighing in on this.  I'll no doubt be needing a little more advice on a few more things in the near future.  So keep those computers and large brains working. 

Your system is old enough that it may have IDE as opposed to SATA connections (or a combo of both).  Check first, as you won't be able to use any new SATA drive with an IDE connection (unless you use an adapter of some sort).

All good advice here. I'll second the idea of 3 drives. I'll also suggest that the sample drive be an ssd. If you have USB 3, you can use a USB 3 SSD. If your sample drive is a mechanical drive it should be 7200 rpm or greater. Don't use a green drive for samples.

JonD, thanks and this is probably elementary, but I'm not 100% sure about my hard drives. I had it built by a gamer/egg head that knew his stuff a few years ago. When I click on the drives properties in Device Mangler, there is no manufacturer or model number. The only info I could glean for both drives is as follows.
ST3500320S ATA Device
Drive C: Capacity 500.000.878.592 bytes 465 GB
Drive D: Capacity 159.891.181.568 bytes 148 GB
So I suspect they are both SATA and not IDE drives, but I'm not sure and don't know much more than that.