Although you may not be jumping for joy that Windows 8 is coming, I'll wager you're at least a little curious. Could the new OS make your computing life any better? Is the new interface a boon, or more of a boondoggle?
Fortunately, you don't have to sacrifice your current PC to find out - nor do you have to buy a new one. You can install the Windows 8 Release Preview alongside Windows 7 and take it for a full test-drive. It's simply a matter of setting up a dual-boot configuration.
Before you go one step further, make sure you have a complete backup of your hard drive, just in case things go wrong. This is a pretty safe operation, but you never know.
The first step is to create a partition on your hard drive, a chunk of space that's reserved exclusively for Windows 8. You'll need at least 16GB, or 20GB if you're loading Windows 8 64-bit, but I recommend giving the OS plenty of breathing room: at least 30-40GB.
This process has been covered many times before, so rather than repeat it here, I'll direct you to Patrick Miller's "How (and Why) to Partition Your Hard Drive."
2. Get Windows 8
Next, you'll need to download the Windows 8 Release Preview. It's available in 32-bit (x86) and 64-bit (x64) flavours. Most modern PCs can run the latter just fine, so that's what I recommend unless your system is more than 3-4 years old. Whatever its age, be sure to check Microsoft system's requirements. Likewise, make note of the product key: TK8TP-9JN6P-7X7WW-RFFTV-B7QPF.
By far the easiest way to install Windows 8 on that new partition is via a USB flash drive. I described this process last year in "How to Put Windows 8 on a Flash Drive," so those instructions should get you squared away.
3. Install Windows 8
Once you've loaded the Windows 8 ISO on your flash drive, boot to that drive. (If your system bypasses the drive and boots straight into Windows 7, you may have to do some tinkering in the system BIOS. Not every PC will boot from a flash drive by default.)
This is the only really critical part of the process. After accepting the installer's software licence, be sure to choose Custom, not Upgrade. Next you'll see a list of available partitions; click Drive options (advanced), then select the unallocated space you created earlier.
Now, click New from the drive options icons. By default, it should display the full amount of the selected partition, in which case go ahead and click Apply.
Finally, click Next to begin the installation process. This will take about 20 minutes, after which your system will boot Windows 8 and run you through the usual initial-setup stuff. (You might have to remove your flash drive so the installer doesn't try to run again. It did on my system.)
From now on, when you boot your PC you'll see a start-up menu that gives you a choice between Windows 7 and Windows 8 - and it'll proceed with booting the latter by default. If you want Windows 7 to remain the go-to operating system, click Change defaults or choose other options while this menu is visible, then click Choose the default operating system. Easy-peasy.
And that's it! Keep in mind that this Release Preview will expire on January 15, 2013, so you've got exactly three months to poke and prod. Have fun!