I bought an Apple Macbook with the educational discounts this summer, with upgrades, a printer and an 30 gig iPod for about what you might pay at a retail store for the computer alone.
I know this is not quite what you were asking for but before you buy you should check out the cost of a new unit with student discounts and see if there are good rebates on additional items you would want or need. I was to increase the value of my already discounted purchase by buying a Canon pixima ip 4200 and iPod at the same time and qualifying for $279 in rebates (free printer, $90 iPod).
As far as making a choice of mac or pc, you can have both with the intel macs. I am using the free beta of 'Bootcamp' to run Windows xp professional on this machine as well as the mac os, with nary a hick-up.
By the way, if you need software, regardless of platform, try OpenOffice.org suite,
www.openoffice.org/, for word processing, database, powerpoint, export to pdf, and a number of other features. It's free and very capable. The fact of the matter is, there is so much good, free Open Source software out there, you probably won't have to buy much software at all.
Software for Starving Students at softwarefor.org/ is a good place to start.
I also recommend you check with your schools IT lab and see if you can qualify for free or almost free Windows software. I am taking a intro to computers course this semester and was able to buy the XP pro disk(s), both regular and 64 bit for $14 plus shipping. I could have downloaded it for free as an iso file but I wanted the disk on hand. There are a number of software packages available and if you haven't taken a computer class yet, it may be worth it to do so.
Cheers