Enable dual boot in Control Panel\System and Security\ System\Advanced system settings

The ISO of the Windows 10 preview can be downloaded from the link provided in the proper page of the Windows Insider Program.

You can use the Windows USB/DVD Download Tool from codeplex to extract the ISO  on a USB pen (must be 4GB+), avoiding to waste a DVD.  After the USB Tool finished creating the boot drive, restart your computer: note that it is VERY IMPORTANT. DO NOT SIMPLY RUN SETUP SINCE IT WILL OVERWRITE YOUR CURRENT OS but to restart and boot into the USB drive. Then you will be given the regular Windows installer window. (see also here for more details)

Note that sometime a new release could introduce some undesired problem, especially if you are a programmer: for example it seems that the March pre-release 10044 introduced some problems in debugging with Visual Studio (and perhaps that it is why in the MSDN there is still the 9926 pre-release). Then you can possibly configure your PC to have a dual boot. To properly install that preview on a new partition in the HD of your Windows 8.1 PC you can follow one or more of the following links: link1,  link2, link3, link4

Enable dual boot in Control Panel\System and Security\System\Advanced system settings

The OS preview Build 9926 takes about 23 GB of disk space, so you need to install it in a partition of at least 30GB … even thought I suggest to have a bigger one (let’s say more than 100GB if you have enough space on your disk) if you think to make some development: you can always easily shrink that volume in a second phase if you want, while extending it could be more complex and time consuming if there is not contiguous unallocated space (in that case, the Extend volume… right mouse option is disabled and you need to use some external tool like AOMEI Partition Assistant [even the free Standard Edition].

As Gabe Aul wrote, based on Windows Insider feedback, Microsoft is going to send out builds more frequently to Windows Insiders that have selected “Fast” preview builds. That means you can getting fresher code with all of the features and fixes, more often – but builds may include more bugs. Read his blog for more details. To switch to slow or fast builds on your PC, go to Settings>Update & recovery>Advanced options. On your phone, go instead to the Windows Insider app.

Slow or Fast build selection

Other good suggestions from Gave are:

1. Go to the Insider Hub in the Start menu on your PC for the latest updates, including new features (like the new Office preview apps) and simple workarounds to issues you may encounter with the new builds. (A Hub for phones is coming soon.)
2. Check out the new Get Started app (also in the Start menu) that guides you through the latest features.
3. Go to the Windows Insider Community forum to connect with other Insiders, get tips and advice, and help solve problems.

For developers: the Windows 10 developer tools are now available and provide an early look at the tools and features that are coming with the Windows universal app platform. See how your apps can take advantage of new Windows capabilities and social integration to create experiences that delight your customers, whether they’re running on a phone, tablet, or PC. Application developers can get Insider access to Visual Studio 2015 CTP6 and the tools, including SDK, here. Hardware developers can get access to tools here. (English-language availability only). See also:
– Windows 10 Technical Preview universal app samples.
– Steps to install Windows 10 development tools for Visual Studio 2015 RC

For IT pros: Have questions about drivers, virtualization, and multi-boot scenarios? Ready to try the in-place upgrade process? Need help with a specific setup or installation problem? Check out these TechNet resources:

• Windows 10 Enterprise Technical Preview: FAQ for IT professionals
• Try it out: Windows 10 Enterprise Technical Preview
• Windows 10 Technical Preview IT pro forums
• Windows 10 for Enterprise: More secure and up to date

Especially if you are using a CPT like Visual Studio 2015 CTP6, it is convenient for you to enable the dynamic content that is displayed on the Start Page:

1. Tools -> Options
2. Under the Environment node, select “Startup”
3. Check the box to “Download content every:” and select your interval.
4. Click OK: your content should immediately start to populate in the VS startup page.

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In the following there are some useful links if you want to study and start developing for the new Windows 10 platform (and the related Windows Phone 10 one!):

• A Developer’s Guide to Windows 10 Preview (free Microsoft Virtual Academy course): (29/5/2015 – now that course is substituted in the MVA by the new one  A Developer’s Guide to Windows 10 – available also here on Channel 9). Anyway, the preview version of the course is still available in Channel 9 at this link (even though it was recorded for a early preview, I think that some lessons remains useful, for example the ones related to Maps, Pen&Ink).
• Community Days 2015 (slide & code) [Dream again with Windows 10 – G. Sardo; DEV02 – MVVM in Universal App; VS01 – Le novità di Visual Studio 2015; WIN05 – I Nuovi controlli e la gestione del Layout in Windows 10; WIN08 – Sqlite nelle Universal App; WIN04 – BT Low Energy in Windows e Windows Phone]
• Windows Insider program (Guide to Windows universal apps; Windows 10 Technical Preview for phones and PCs)
• Windows 10 Technical Preview tools
• Windows 10 developer tooling preview now available to Windows Insiders

Samples

• Windows 10 Technical Preview universal app samples (GitHub – Windows-universal-samples) (see this post on GitHub if you need some more info how to use and sync a project)
• Matteo Pagani GitHub Windows 10 samples
• An Introduction to Building Windows Apps for Windows 10 Devices (Download the Code Sample (VB)) (Template10)
• Using #mvvmlight with Windows 10 universal applications ; Prism evolution toward Windows 10 (GitHub repository PrismLibrary/Prism)

You can also have a look to my previous posts on Universal App development:

• Windows Phone 8.1 – Some useful links for developing Windows “Universal Apps”;
• MVVM frameworks for Windows RealTime (Universal Apps): which one to choose?

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NOTES

Enable your device for development

With Windows 10 Insider Preview Build 10074, developers cannot enable Developer Mode in the Settings app for installing and testing apps on this build. We’ll enable this in an upcoming build. In the meantime, you will need enable your device for development using the Group Policy Editor (use of gpedit to enable your device):

1. Open a cmd prompt with administrator privileges.
2. Run Gpedit.msc.
3. Go to Local Computer Policy > Computer Configuration > Administrative Templates > Windows Components > App Package Deployment
4. Edit the policies to enable the following:
   • Allow all trusted apps to install (Enables your device for sideloading apps)
   • Allows development of Windows Store apps and installing them from an integrated development environment (IDE) (Enables your device for development from Visual Studio)
5. Reboot your machine.

In next releases, the “For developers” section will be used for setting that features …

Local Group Policy Editor

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Update for Windows preview build 10074 and VS 2015 RC

As stated here, if you are using a different development environment than Visual Studio 2015, you can download a standalone Windows 10 SDK installer BUT you don’t need to do it if you’re using Visual Studio 2015 – it already includes the SDK. However, if the emulators are not working properly, an alternative solution suggested in the MS Developer forum, is to install the Windows Emulators separately (https://dev.windows.com/downloads/windows-10-developer-tools ): scroll to the bottom of the page and install the and Windows 10 emulators outside of Visual Studio setup). BECAREFUL: I tried to install also the  Windows 10 SDK but, after doing that all the Visual Studio environment broke (even a new blank solution didn’t compile anymore because something was missing) … so I had to reinstall all the Visual Studio environment!!

The xml file defining the UAP of our platform is in C:\Program Files (x86)\Windows Kits\10\Platforms\UAP and the available extension that can be referenced in our project are in C:\Program Files (x86)\Windows Kits\10\Extension SDKs .