Consider that you can buy an external hard drive with a one year warranty but the drive inside the case may be the same one that carries a three year warranty if you buy it separately. Bundling is about making the total price look more attractive but it does come with a downside. Warranties are not free either. The probability of failure and the cost to cover such is computed in the same way insurance actuaries work and that cost is built into your purchase price.
My wife purchased a Dell desktop system from Best Buy last year (May 2009). The monitor died on it earlier this summer. Apparently, Dell's "3-year warrantee" on monitors does not extend to monitors purchased with entire systems, they only carry the one year warrantee that the tower has. First of all, a one year life expectancy on a monitor is a tad short. Second, not honoring the typical warrantee extended to monitors purchased separately is poor business practice. Lastly, if this is the sort of support I can expect from Dell, I'll likely not be purchasing another computer through them... either for personal use, or through the university at which I'm employed.

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