Hey Haleyhales,
First off, I think that you should get around 80-100GB of 5400 RPM storage. And then purchase an External Hard Drive just in case that gets filled up.
Do you mind posting some of your computer's specs?
Dual core processors are the newest Intel Processors and they're actually going to undergo a price cut mid-May, meaning you can probably get a great deal on them by the time your graduation rolls around. Basically, think of a solo core processor as one person juggling however many tasks you want them to juggle. Now picture a dual core processor as two people juggling the same number of tasks. That's pretty much the simplist explanation I can think of, and it doesn't really do the processor justice, but that's what it essentially is.
As for Dual-boot, that refers to some new technology that Apple has rolled out that enables users to install both a Mac operating system and a Windows Operating system onto their computer/laptop. While this may seem like a great reason to purchase an Apple, I would advise against it as the Windows does not work seamlessly on Apple as of yet--it's probably going to take a while until the level of integration is on par with Windows-intended laptops.
As for processors, This is a link for processors that's from notebookreview.com's forums that really clears up a lot of things.
http://forum.notebookreview.com/showthread.php?t=24051
The only explanation that guide to processors is missing is an explanation to Dual Core Processors, but I think I've explained the gist of it well enough. Oh yea, AMD is also coming out with a mobile version of their dual core processor as well, so be on the lookout for that.
I know I've said a lot, but I wanted to tell you this as well:
I doubt that a College Student needs to possess the latest-generation hardware. When those newfangled processors come out, I think it's wisest to opt for the second-generation processor, such as Pentium M, because those types of processors are most likely to be much cheaper while in the shadow of their stronger brethren.
For example, I recently purchased a Dell XPS M140 with a Pentium M 740 [1.73 Ghz], 1 gb of RAM, 120 gb Hard Drive and a 9 cell battery[which gives me about 6+ hours of battery life]. I'm pretty confident that this will last me throughout my college years, and even if it doesn't, I can always replace the parts myself [or if you don't want to, you can get a tech-savvy friend to do it.]
I also want to clarify any confusion you might have over Centrino Technology. Centrino is not a processor, but it denotes a combination of Intel Technology. If I remember correctly, it denotes the combination of Intel Wireless, Intel Processor, and Intel Chipset Motherboard. Centrino Duo just means that the Processor is a Dual Core Processor.
I really hope this clarified some things for you.
But if you wanted me to shoot out a product suggestion, here it is:
$1000 Budget: Dell XPS M140
$1500 Budget: Dell E1405 [This model actually isn't out yet, but it's going to be out by the time you graduate]
$2000 Budget: Dell E1405 with better specifications
$2500 Budget: Thinkpad T60
If you do choose Dell, remember to use the Online Coupons that they provide for you. Notebookreview.com has a bunch of them.
I really do hope this helps.