Computer Advice for incoming (or old) students

Questions to ask yourself:

Desktop or laptop?
Windows, OS X or Linux?
Do you plan on using your computer for something other than homework (games or such)?

Desktop or Laptop ?

Answer to this depends on the way a student works - from home/dorm or school. Another critical factor that influences this is the amount of travel. Personally, I have both - initially I just had a desktop but laptop gave lot of flexibility while travelling (attending workshops/conferences, etc) and helped me make learn a lot more from such events. Currently, my desktop, apart from being used for research/sys-admin related purposes, runs my webserver; while my laptop serves as my mobile work place.

Windows, OS X or Linux?

Depends on whether packages/software you need for your work (school/home/entertainment, etc) are available for that particular platform and more importantly, how comfortable one with it. Personally, my deskop is a pure linux box (Red Hat Enterprise Linux), laptop used to be a dual boot (Windows XP Home and RHEL) but I have now moved over to Mac laptop...