The first change was the continued maturation of desktop Linux. Today, no one can argue with a straight face that people can't get their work done on Linux-powered PCs.
Ubuntu, PCLinuxOS, MEPIS, OpenSUSE, Xandros, Linspire Mint, the list goes on and on of desktop Linuxes that PC owner can use without knowing a thing about Linux's technical side.
People can argue that Vista or Mac OS X is better, but when Michael Dell runs Ubuntu Linux on one of his own home systems, it can't be said that Linux isn't a real choice for anyone's desktop.
Another change occurred when Nicholas Negroponte proposed the so-called $100-laptop, the OLPC (One Laptop Per Child) machine.
He couldn't get them built for quite that price—they cost about $200—but that's still remarkably cheap and they're available today.
Not long after OLPC was announced, Intel and other companies came up with their own take on an inexpensive PC: the Classmate PC. By 2007, it had become clear that you could build a laptop that was good enough to run desktop Linux for about $200.
That gave other hardware vendors an idea.