Which Macs can boot Windows?

All of the Intel-based Macs can boot Windows. This includes the MacBook, MacBook Pro, and Mac Pro models as well as Intel powered systems from the iMac and Mac mini lines. Intel-based Macs also can run Windows, or Windows programs, through a "virtualization" solution like Parallels Desktop for Mac, VMWare Fusion, or CrossOver Mac.

Which versions of Windows can you install on an Intel-based Mac?

The original "XOM hack" made it possible to install the 32-bit version of Windows XP Pro. One user in The OSX86 Project forums modified the originally released hack to work with Windows Media Center 2005 as well.

Officially, Apple Boot Camp was designed to install Windows XP Home SP2 or Windows XP Pro SP2. However, visitors have reported installing Windows Vista, Windows 98SE, and Linux, as well as Windows XP. Bloggers also have installed Windows 2003, Windows Media Center Edition, Windows Tablet Edition, Windows Vista, and Sun Solaris.

Parallels Desktop for Mac supports effectively every version of Windows, as well as Linux, FreeBSD, OS/2 Warp, eComStation, Solaris, and MS-DOS "in secure virtual machines running alongside Mac OS X". MacOnIntel also reported installing NeXT OpenStep.

Will a Mac running Windows be subject to Windows viruses/spyware?

Yes. It is important to recognize that an Intel-based Mac when booting Windows is for all practical purposes the same as a Windows "PC".

On one hand, if Windows is installed and running on an Intel-based Mac, the system can take advantage of additional applications and games that are available for the Windows platform, but it also can be compromised in the same ways that can harm any other Windows PC.

In the company FAQ, Parallels likewise notes that:

Parallels Desktop for Mac runs the guest OS in a special virtualized environment that emulates a separate computer. This virtualized computer is as vulnerable to the viruses as a usual PC running Windows. We highly recommend that you install some anti-virus software and firewall in the guest OS."

For more information, please also refer to "Can Windows viruses on an Intel-based Mac damage MacOS X?"

Can you install Windows on an external drive with an Intel-based Mac?

Not officially with Boot Camp. On page 7 of the "Boot Camp Beta Setup and Installation Guide" Apple reports that Windows XP "requires its own partition on your computer's internal startup disk."

However, various users on the WinXPonMac forums have discussed unsupported workarounds.

Can you install Windows on a recent PowerPC-based Mac?

Recent PowerPC-based Macs cannot boot Windows like Intel-based Macs. However, these systems are capable of running a variety of versions of Windows in emulation, which is substantially slower.

The best known solution is the discontinued Microsoft Virtual PC 7 which is available both with Windows XP Home and Windows XP Professional. Microsoft describes the software as "the application that makes it possible for you to access PC-only software, files, networks and devices from your Mac" and notes that version seven is "compatible with [PowerPC G5-based systems and] offers important improvements in support, speed and reliability."

You also might wish to evaluate OpenOSX WinTel and Lismore Guest PC.

OpenOSX WinTel is available in a "smart Universal Binary" to run on both PowerPC-based and Intel-based Macs. Rather than emulating Windows it provides "full Pentium emulation". It ships with a variety of open-source operating systems, but commercial operating systems such as Windows can be used as well. The website notes that Windows XP is compatible, but recommends Windows 98 for PowerPC-based systems.

Lismore Guest PC also emulates an "x86 PC", comes bundled with DOS, and is ready for you to buy and install Windows with a "built-in Windows Setup Assistant".