My $0.02 on matters discussed in this thread:
(1)
Buy a laptop.
Get something reasonably fast, equipped with Office and an IDE that does
C++. I've found that a simple but reasonably flexible graphing calculator application (one comes bundled with Mac OSX, don't know about Windows) can come in handy at times also.
There's just so much coding in the program, or Excel work at a minimum, and you'll want to be able to carry it with you easily. While you're at it, get an external hard drive and make regular backups.
(2)
Don't buy a Dell.
Made this mistake once in buying a laptop for my wife (then fiancee); thankfully, she consented to marry me anyway. It was too little machine for the OS they shipped it with, and when I tried to upgrade, I discovered they had taken up both memory ports with the smallest SIMMs they could find, so I had to buy two new chunks of memory, not just one, and throw the old ones away. If you must go this direction, be very careful about what you're buying.
My wife's next laptop after the Dell was a teeny-tiny Sony Vaio that she likes as much as anyone can like a machine whose OS was written by Microsoft.
(3)
Don't dismiss Macs.
For some reason they've been passe in scientific computing circles, but I've been an Apple guy since my family got a II+ in 19 something-something. They rule. The OS is UNIX-based, and it's written by the same company that makes the hardware, so they're orders of magnitude more stable than PC's. I confess to liking the fact that the OS is simpler; with far fewer tweaking options available, it's possible to actually find what you want in short order. Anyone who's ever installed a new piece of hardware on both a PC and a Mac is just downright deluded if they deny that the overall execution of Mac OS is better.
Macs come with a
free full-featured downloadable IDE that does
C++, Java, and
Python. They use the public-domain GCC compiler for
C++, so the code you generate is quite portable. Thanks to their (distant) second market position, they're virtually virus-free and have been forced all along to communicate quite well with PCs. The support you get, if you do have a problem, is absolutely unparalleled. The one time I did have a problem with my current Mac (some bad third-party memory), I made an appointment at the Genius Bar down in SoHo and got
free support that saved all the material on my hard drive. (At that point, I needed another Mac to be able to pull the material off my hard drive, so obviously phone support would not have done the trick.) I still sort of can't believe they didn't charge me for it.
At the top of my to-do list once I have a full-time job is to pick up one of the new Intel-based Macs with Boot Camp. I'm really looking forward to the day when Macs run Windows-based applications faster than PCs do.