Top 10 Warranty-Voiding Hacks. @neverbeenback: As was said down below in the comments, many warranties state that you can't change the OS to something 'not approved' which is generally a few versions of windows.
Wether or not the company *actually* voids your warranty is up to them. edit: hackintoshing is vaguely illegal as well, so I can't see Dell being psyched to help fix your hackmac. Top 10 Warranty-Voiding Hacks.