Windows 10 preview is available to download and test , .net is required whether you are using some application that require .net2.0 or .net3.0 , or you are developing something that is targeted to .net2.0 or .net3.0 , you have to install .net in windows 10 , let me walk you through the steps how to install .net in windows 10 preview .

Steps

1. Mount “Windows Installation Media ” ( i.e ISO or DVD or USB )
2. Click on “Start”
3. Click on “All Apps “
4. Click on “Windows System”
5. Right click on “Command Prompt ” and open as “Administrator “

6 . copy and paste following and replace d: with your mounted drive letter .

DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:d:\sources\sxs

Wait until it finish installing then , essentially restart your system . and yes if it stuck while installing just hit enter couple of time (believe me it worked ) .