Advantage to whom?
As a software developer, I get a lot of use out of keeping a PC that can also boot Windows XP (you know the drill: have to use customer's Windows only VPN software, want to try Windows applications, etc.)
I was fortunate, my Dell(*) Ubunto Linux/Windows XP PC has been having no problems, when booted to Windows XP, getting software updates - but some people have not been so fortunate. I believe that Microsoft has a potential customer relations problem, but it is a mild problem - but with a long tail: customer frustrations with a product and vendor do add up, and incur a long term cost to the vendor.
Most consumers are stuck with Microsoft, unless they buy a Mac - but the cost of a Mac is so much more than PCs with similar performance.
(*) No, I did not actually purchase a Dell - a very nice customer ordered one for me as a gift (they buy a lot of Dells, and the discount cost to them was not too much money).