Because you have as you say one HD, I think you will find the benefits of having them seperate partitions will not be anywhere near as good as if you have seperate HDs, because the Data still comes from one source, along one cable.
Having seperate HDs will make it far, far quicker.
I dont give a stuffed monkeys what anybody says about that, I have several PCs and they all have at least 2 HDs, and in all the tests I have done,having more than one HD has proved time and time again, that the PCs run quicker, or at the very least, they feel quicker, and this can make all the difference.
As an example, and I have said this many times over in this, and other forums, if I have 2 HDs, Then they each have 2 partitions each.
Drive 1 =
C: = Windows
E: = Media
Drive 2 =
D: = Apps
F: = Junk
This is how I always have it
Having a seperate partition for a Swapfile is also proved to be a non-usefull idea especially if its on the same drive as the system ( C: ), and having it on a seperate HD altogether does help, but this is a small ammount really because Windows is designed very much to use one, so it will use one if it needs to regardless of whether you use one, how big it is, where it is, or whatever, if Windows wants one, it makes one... I myself split them up... One swapfile per Drive, not per partition, and I make the one on C: fairly small... Usually about 256MB is ample with the rest in the above example, being on D:
To be honest, the Swapfile has been the basis of long arguements over the years, but in truth, there are just as many people who can point you to sites that say one thing, as there are those who can point you in other directions that say another, so really thats up to you where you put it.
Now, with your Apps on one partition, and the system on another, in terms of speed, this wont help much at all, it will help with fragmentation however, and this will make that difference, but to be honest, a seperate HD wil make it all the more.
In my main Machine, I currently have a Raptor as C: ( 8GB ) and the rest ( T: ) is for my Setup files... Such things as ISOs of game CDs and DVDs and other stuff ready to install... I did this because I will rarely use both C: and T: together at the same time, unless I am installing something, and I mostly install to D: anyway, so the time I spend accessign C: and T: are minimal.
D: is my Apps and Games.
I install games to D:\Games\Gamename and pretty much everythign else to D:\Program Files\ and this I do simply by changing the C: to a D: when prompted, and I have other stuff on there of course, like a BenchMark folder, and inside this is things like Prime, SuperPI, as well as 3DMark etc, and also a Drivers and a SysTools folder for drivers and system tools for all my systems. Very logical and it rarely needs defragging, unlike C:
I also make a point to NEVER install anythign to the root of any partition... There is nothign wrong with that, but I like my root directories to be as clean as possible.
My E: is always Media.
I have severla thousand MP3s, same with MidiFiles, and SoundTracker Mods, as well as hundreds of Movies etc and E: was last defragged in February and on checking it, I have .... 7 fragmented files - Enough said.
F: however, I use for everythign else ,such as downloads, Backups of My Documents, and well, you name it... This does get fragmented every 5 minutes, but guess what? - Using O&O DeFrag 8, I defrag it, and its defragged in a few minutes and it does not affect the PC speed in one tiny little bit...
I am downloading torrents 24/7, as well as defragging the same drive F: ( 40GB Maxtor ), I am burning 3 DVDs at a time, as well as playing BF2 or HL2 or Doom3 etc and converting a DivX / AVI file to DVD/MPG, and I get absolutely no problems or slowdowns at all.
If I had one HD with more than one partition, I could not do what I need it to do, and its not all down to CPU speed either, because my Barton does this just fine too... It just slows the background stuff a lot more thats all, but otherwise, games etc still play just fine.
Anyway, I have gone way off track here.
The Swapfile will benefit from being split over the two yes, btu dont expect the difference to be massive.
Try to have Windows and Apps on a different Drive, and perhaps shrink C: and make the extra partition made up on that drive to hold your lesser used data, such as Media... Because when you are playign the Media files ( Music / Movies ) you are not really needing the full potential of your HD are you, so you should not see any slow downs at all, plus only having Windows on C: will as I said earlier speed up thigns like defragging ( I defrag C: in way less than 1 minute )
And yes, the cache does not really make that much difference, of my latest HDs I have a WD thats got 16MB and a Hitchi thats got 8 and the hitachi is way quicker than the WD. The 2MB caches are even a little weird because the Maxtor 40GB drives are only 2MB and yet, I find them very quick as an F: for dowloading etc, but not as good for C:
I hope that will do for now, cos I am wafflign far too much, so I will drop it there for now.