MakeItSo,
I think there is an easy way of doing that: Remove the "OEM" type operating systems from sale, and give the purchaser the option of say, Windows XP or Linux with an appropriate software bundle, and a price difference that reflects the costs to the manufacturer in support and actual purchase costs.
In the UK earlier this year, a well known computer maker tried this, offering Linux PC's with OpenOffice, but it fell down after a few months because:
1) the Linux machines weren't able to use all the features within the PC (eg the USB only ran at 1.1 rather than 2, PCI software modem didn't work and the graphics card didn't run at top resolution/refresh rate for the supplied monitor).
A little work on their part could fix this, with appropriate drivers and configuration.
2) Their technical support staff, which already didn't have a particularly good reputation amongst the UK computer population, could write what they knew about Linux on the back of a stamp, and were ill prepared for the associated support calls.
They stopped doing them after about 3 months.
John