Tak si o tom nieco precitas najprv, aj ked to nabizi
http://windows.microsoft.com/en-us/windows/preview -faq

Unexpected PC crashes could damage or even delete your files, so you should back up everything. Some printers and other hardware might not work, and some software might not install or work correctly, including antivirus or security programs. You might also have trouble connecting to home or corporate networks.

Some installed apps might not yet work as expected or might not be available in your country or region. For example, Cortana is currently only available in English (United States). To be able to use Cortana, the country or region for your system must be set to United States, and you also need to have installed the English (United States) version of Technical Preview.

Also, if your PC runs into problems, Microsoft will likely examine your system files. If the privacy of your system files is a concern, consider using a different PC. For more info, read our privacy statement.