In an interesting turn of events, Apple (the maker of Mac OS X—the world's best Operating System) has announced that they will not be using PowerPC processors anymore. Now they will be using processors designed by Intel (the company that designs processors used in most Windows-based PCs.
I don't yet know quite what to think about all this, for a few reasons. First of all, it would almost be insane for Apple to give up hardware production, so I don't think anybody will be able to install OSX on a run-of-the-mill piece of junk Dell computer. Second, Apple can't yet count on OS X sales alone to drive Mac acceptance, simply because not enough people know about OS X's advanced and far superior (than Windows XP, Longhorn, or any other PC operating system) abilities.
I would venture to guess Apple will use most of the same internal architecture for their computer hardware, replacing only the CPU and related chipsets and power supply circuits. This would allow Apple to transition hardware-wise easiest, and still maintain most of the important hardware-related code (i.e. for chipsets, hardware addressing, etc.) that makes Macs run so efficiently and speedily.
Apple announced that they've been developing Intel-compatible versions of Mac OS X for a few years now, so the software does not have any major hurdles to Intel compatibility, and Apple is also helping developers transition with a special package of tools for developers. Apple even displayed many demonstrations of Tiger (the world's most advanced OS) on 3.4 GHz Pentium 4 processors.
What I don't yet understand is how Apple will advertise this switch. With the G5, Apple went to 64-bit processing; will Apple take a step backwards to a 32-bit Pentium 4 processor, or does Intel have a good 64 bit chip that will be up-to-snuff for Apple's purposes? This will be an interesting transition to watch over the next few years, to say the least!