At the moment, if you want a Windows-based machine, I’d suggest running WindowsXP – if you have to buy a new laptop in the near future, this is a good idea, and I think you can still buy one with WinXP. Ask Dell first if they will do it. They are the best of a bad lot for support – DO go for their service packages if possible. Lenovo (was IBM) might be a good second option to try after Dell.
Vista (the new version of Windows) is problematic. Some of the problems (e.g. hardware with drivers that won’t work on Vista, even if they are designed to) will be solved in time (I guess 3 to 9 months). The ones that remain will be about “DRM” – ways that Video and Music files are restricted to the person who legally owns them: Vista is very picky about them, and is known to stop your sound card and/or video card working if it thinks you don’t have the rights to the music or video – and it often thinks you don’t have the rights to the music or video, even if you do but you’re using legitimate copies or you’re using versions without DRM etc. Boo-hiss Micro$oft.
Eventually however, WinXP won’t be available, and eventually won’t be supported by new hardware and software, and eventually won’t be supported by Microsoft.
If you can possibly find the money initially, an Apple MacBook is a good option – more expensive initially (though there is a student discount at some places e.g. krcs.co.uk), but cheaper, faster, more reliable, more secure in the long run.
I recommend OpenOffice.org – a free open-source equivalent to MSOffice. It can open and save in all the MSOffice formats, except for the newest one, and that is about to be solved in the next release. It comes with equivalents of Word (called Writer), Excel (called Calc), and PowerPoint (called Impress). You can download it at www.openoffice.org It is similar but different. Though the newer versions of MSOffice are more different to Office 2000/XP than OpenOffice.org is.