After installing a new windows os almost everybody goes through unexpected error.
Because most of the time we install all required softwares which we had earlier with same versions. So sometimes it’s the compatibility issue. But your problem looks easier to solve.
You need to open a new commandline (by pressing Win+R => cmd.exe) and after that try to enter "java". I am very sure that you will get the error that is like "command not found". A reason behind this error is that you forgot to set an windows environment variable for your java.exe.
You can very easily set it by following below procedure
Go to Win+X => System => Advanced System Settings => Advanced => Environment variables => then search for PATH under your system variables => edit => append the path to your latest in use java.exe separated by ;
For e.g.: ../other/pathes/with/file.exe;C:\Program Files (x86)\Java\jdk1.6.0_45\bin
Finally Save, close, and restart your box.