To try out the Windows 10 Technical Preview - a very early version of Windows 10 - on your Mac, you don't need to already have Windows on your Mac. In fact, it's relatively easy to install the new Microsoft OS. Here's how to try Windows 10 for free on your Mac.
Two options
There are two ways to get the Windows 10 Preview on your Mac. The first is to install Windows on a separate partition of your hard drive using Apple's built-in Boot Camp software. When you're done, you can boot directly to Windows. In this way, your Mac is basically transformed into a full Windows PC. Also read: 15 useful tips for Windows 10.
Another option allows Windows to run as a virtual machine within an OS X program. We're using Oracle's open-source VirtualBox here, but Parallels Desktop is a popular alternative (but costs about $80). A virtual machine is the way we recommend, as the Windows 10 Technical Preview is still in its very early stages, with some rough edges and bugs. If something goes wrong on a virtual machine, it won't affect your hardware or OS X installation - you can just erase it and start over.
As with all pre-release software, different people's experiences may vary. I had few problems: I installed Windows 10 on a late 2014 MacBook Pro with a 2.6GHz i5 processor and 8GB of RAM. A recently released Mac should be able to run Windows 10 just fine.
Whatever you do, back up your Mac's data first. I already mentioned that the Windows 10 Technical Preview is very flimsy and experimental... You don't want to lose all your valuable documents and family videos if Microsoft's operating system gives you problems.
Download the ISO
Ready to back up? First we go to the Windows 10 download site to download the Technical Preview. You will need to sign up for the Windows Insider Program by giving Microsoft your email address.
After registration - heed all warnings that this is pre-release software and Microsoft's warnings that you should back up your data - you need to select the version of Windows 10 that suits your system. If you have a relatively new Mac with an Intel processor, opt for the 64-bit version. It's almost 4GB so sit down - the download may take a while. Also write down the product code; we didn't need it for our test version, but it's handy to have it just in case.
Install Windows 10 in VirtualBox
Let's first explain how to get Windows 10 running in a virtual machine, as this is our recommended method. Go to the Oracle VM downloads page, and select the VirtualBox suitable for OS X hosts.
Start the download by dragging the icon into the Applications folder. A 300-page PDF is included if you want a detailed tutorial - but you can skip it and keep reading this how-to if you don't have the time or inclination to actually learn all about VirtualBox.
In the VirtualBox start screen you have to choose which operating system you want to install. I chose Windows 8.1 because that is the most recent version of Windows listed in the drop-down menu. Windows 8 would probably work too - just make sure you choose the correct 64-bit or 32-bit option, depending on the version of Windows 10 you downloaded.
VirtualBox will then ask how much RAM you want to allocate to running the virtual machine. You can choose the default option of 2048MB if you're concerned about system resources, but Windows 10's performance will improve if you allocate more - because you're running another operating system at the same time. If you can increase it to 4GB that would be perfect.
You will then be asked to create a virtual hard drive for Windows 10. Unless you plan on doing extensive work or installing more software, you can safely select the default 25GB. Select the VirtualBox Disk Image option on the next screen and continue.
After that, you have to select a dynamically allocated or a fixed hard drive. As you can probably tell from the context, the former grows as you add more space. This is a better choice if you're short on space and don't plan on adding much to your "Windows computer". However, the determined drive gives faster performance as long as you have the space.
