Actually, a great tip to save yourself money on any computer purchase is to use any and all FOSS (Free and Open Source Software) that you can get your hands on. Most Linux Operating Systems (and BSD systems too) are FOSS, free to use and manipulate as you please. Most software (like OpenOffice or KOffice, GIMP (like Adobe Photoshop) are FOSS as well. Just think, most, if not all software available for Windows has a FREE Linux counterpart, which for 90% of users will not entail any loss in features. I know that some serious graphic arts professionals feel limited by GIMP, but most most of us masses, FOSS software gives everything (and more) than we ever need or want, for FREE!
Also, many many many FOSS programs are ALSO cross-platform. What does that mean, it means there is a Windows version too!!!
So if you already have sunk money into your OS or are way too afraid of changing, you can save yourself some money on new software, by looking into FOSS software before you purchase any more software.