Windows 7 and Snow Leopard are great. And cheap. Boot Camp's the free, official way to run them both natively on one machine. It's easy to setup, and just works, except when it doesn't. Here's how to survive Boot Camp.
Boot Camp, to be clear, is different from virtualization software like Parallels or VM Ware Fusion or Virtual Box, which you let you run Windows inside of OS X, almost like an application. Boot Camp runs Windows natively on a Mac—you power on, click the Windows icon at the boot manager, and it starts it up, just the same as if you'd powered on a Dell. Why Windows straight up on a Mac? To live a little. Or in my case, to play PC games.
• A Windows 7 disc
• A Snow Leopard disc
• An Intel-based Mac
• Free disc space!
More on system requirements here.
Boot Camp, and the process of installing Windows in most cases, couldn't be more straightforward, at least as far as operating system installs usually go. After you've got your Mac up and running like normal, fire up an app called Boot Camp Assistant (just use Spotlight). It'll warn you to back up your disk before installing Windows, which you should, since you are asking favors of the hard drive gods here.
Boot Camp Assistant will ask how much of your hard drive you wanna dedicate to Windows. You want more than the laughably small 5GB of space it suggests. Since I keep around 3-4 games on my Windows partition at a time, and I want some breathing room just in case, I stick with 40GB, but you probably really want no less than 20GB. Slide the bar toward the Finder face, granting Windows how much hard drive space you want it to have. After you click partition, Boot Camp Assistant will start getting your hard drive divvied up for some Windows action, which'll take a few minutes. Once that's done, you'll need your Windows disk.
If everything went according to plan, skip this next section!
It's possible you'll get an error that says Boot Camp Assistant wasn't able to create the partition because some files couldn't be moved, and you need to format the drive into a single partition. Basically, what's happened here, most likely, is that your hard drive is fragmented like a mofo, and there's not enough contiguous space for Boot Camp Assistant to create the Windows partition. Yeah, disk fragmentation. In OS X. Believe it. From here, there a couple possible solutions.
If you're extraordinarily lucky, it's possible you might be able to simply restart your computer and stuff will just work. Probably not! From there, you proceed to the free and easy solution. Using Disk Utility, resize your main OS X partition, reducing it by 40GB (or however much you plan on making your Windows partition). Hit apply, and pray. If that goes peachy, you'll have 40GB of unused space on your disk. Go back to Disk Utility, and re-expand your OS X partition to reclaim the 40GB. After that's all done, run Boot Camp Assistant again, and since the hard work of moving files around on the disk was done by Disk Utility, you should be golden.
If, on the other hand, Disk Utility also refused to change your drive's partitions, you have two choices. The nuclear option is to back up, format your hard drive completely, then run Boot Camp and divide your hard drive into partitions from the Snow Leopard installation before restoring all of your OS X data via machine. Since my Snow Leopard install was practically virginal, as a totally clean (not restored) install that was only around 10 days old [ed. note—how the hell did your hard drive get so fragmented then?], I said screw that. Which led me to iDefrag.
It's a $30 defragmenting program. I don't know if my hard drive was really as disgustingly fragmented as it said, or if it'll ultimately help my Mac's performance, but it perfectly executed what I bought it for. Basically, you make a startup DVD (using your Snow Leopard install disc, so keep it handy), boot into it, and it shows you how gross and fragmented your hard drive is before going to work defragging it for a couple hours. Restart, you're back in OS X, and Boot Camp Assistant won't talk back to you again. At least, it didn't to me.
Okay, welcome back, people without problems. After the partioning is successful, Boot Camp Assistant will ask you to pop in your Windows disc. If you've got one of these Macs and 4GB of RAM, you should install the 64-bit version. If not, go 32-bit. Now, all of the pains and glories of installing Windows will actually commence.
After you pick the language and accept the terms, it'll ask you want kind of Windows installation you want. Pick custom, and you should get a list of hard drives to install Windows on. Make sure you highlight the correct partition and click format, which will transform it to Windows' native NTFS file system, if you're doing a partition that's bigger than 32GB for Windows. Then tell Windows to install itself there. Go make a drink, and come back 20 minutes later.
Welcome to Windows land.
To pick between booting into OS X or Windows when you turn on your Mac, start holding down the Alt key before the gray screen appears when you power on. (You gotta be fast.) It'll give you the option to boot into Mac or Windows. Pick Windows, obviously. Once you're totally in Windows, like with the desktop and everything, you need to pop in the Snow Leopard installation disc, and run the Boot Camp installer, which puts in place all the drivers Windows needs to actually run decent on your Mac.
After that, you should run Windows Update to grab the latest goods from Microsoft, and I'd suggest, especially if you're running a unibody MacBook (or Pro) going to Nvidia's site and downloading their latest Windows 7 drivers for your graphics card (the 9M series for unibody MacBook Pros, 8M for the previous, non-unibody generation).
Overall, Boot Camp 3.0 in Snow Leopard works way better and more smoothly than before: Multitouch trackpads on MacBooks feel way less janky; shortcut keys, like for brightness or volume, work exactly like in OS X (before, you pressed the function key); and you can read your OS X partition's files from Windows now. (Back in OS X, you won't be able to write to your Windows partition if it's the NTFS format.) By the way, the command key, by default, is mapped as the Windows key, so you're probably gonna annoyingly bring up the start menu a whole bunch. It's natural.