How complicated is it to install Windows on an Intel-based Mac?

It is considerably easier now than it was in 2006, with multiple fully supported options.

Using "XOM"

This answer is provided primarily for "historical" purposes. Users who need to "dual boot" an Intel-based Mac would be better served by Apple's Boot Camp solution.

Referring to the "XOM hack" solution originally provided by creative and hard-working hackers, the first version of the Windows on Mac Q&A published April 3, 2006 said:

If you took a quick look at the installation instructions on WinXPonMac or watched the video "walk through" at blog Uneasy Silence (now both offline), it became immediately apparent that compared to installing the average MacOS X application, installing Windows on the Intel-based Macs was rather complicated.

A MacWorld feature documented the process of installing and using Windows XP on an Intel-based Mac via "XOM". The article should be read in its entirety, but regarding the relative complexity, the author said:

I don't think that installing and using Windows XP on an Intel Mac is at a point today where I could recommend it to anyone other than a hardcore dedicated techie type. If everything goes perfectly, yes, almost anyone could get XP installed on an Intel Mac. But when something goes wrong, which it invariably will given the complexity of this project, you're going to want some technical know-how to at least recover from the disaster, if nothing else. You also have to have a bit of a cavalier attitude about your system, knowing it could be rendered unusable at some point by some seemingly innocent action, like installing a new driver.

Once the project matures a bit, and solves the remaining technical hurdles, I would then not hesitate to recommend this solution to those who need Windows XP access but prefer to keep using the Mac as their primary machine.

For more on the original "XOM hack" method of installing Windows, please refer to the Windows on Mac "XOM" Q&As.

Using Apple Boot Camp

Compared to the earlier method released by hardworking and creative hackers, installing Windows using Boot Camp is very easy.

A MacWorld feature summarized the experience:

One word kept coming to mind Wednesday, as I sat down to install Apple's Boot Camp public beta on my Mac mini Core Duo -- simple. Using the software to install Windows XP on my machine? A very simple process. Choosing which OS to boot? Also simple. Installing the necessary drivers? At the risk of repeating myself, simple, simple, and did I mention simple?

As one would expect, installation and setup for the final version of Boot Camp 2.0 distributed with MacOS X 10.5 "Leopard" was just as easy to use as the beta version and installation and setup of Boot Camp 3.x included with MacOS X 10.6 "Snow Leopard" is as well.

For more on Boot Camp, please refer to the Windows on Mac Boot Camp Installation and Boot Camp Usage Q&As.

Using Parallels Desktop for Mac

Due to widespread public beta testing, the final versions of Parallels Desktop for Mac are straightforward and easy to install and setup. Parallels provides extensive documentation and video tutorials about how to install, setup, and use the program.

For more on Parallels Desktop for Mac, please refer to the Windows on Mac Parallels Installation and Parallels Usage Q&As.

Using VMWare Fusion

Like Parallels Desktop for Mac, the final versions of VMWare Fusion also have been extensively tested and are easy to install and setup. VMWare Fusion documentation and support is comprehensive.