To install node.js in windows I suggest to use nvm, its a version manager for node.js.
Download nvm at https://github.com/coreybutler/nvm-windows.

nvm install {version} {arch}
$ nvm install latest all ## install latest version of node.js (supports 32/64 bit)

$ nvm list
* 4.4.7 (Currently using 64-bit executable)

$ cd mywebapp # go to your project app then SET the node.js version
$ nvm use 7.9.0
Now using node v7.9.0 (64-bit)

If ever you encounter an error “ERROR open settings.txt The system cannot find the file specified.“.
To overcome this error, follow these steps:
1.Go to c:\Users\{username}\AppData\Roaming\nvm directory
2.copy settings.txt and
3.paste it to c:\