One of the things I like about Android compare to iOS is its flexibility. For example, to stream a video on the iPad, one will have to use very specific apps. On Android, you can basically stream or open any types of file with your preferred app.
However before you can do that, you'll need to do some initial setup first, just the way how you would setup the network to access files/folders on another PC in the same network. This guide assumes that a Wifi network is already setup properly in your household.
What we'll do (short version)
1) Share the movie folder on your PC
2) Install ES File Explorer (free Android app) which can access network files
3) Browse and play the movie!
What we actually do (long version)
1) In Windows 7, right click movie folder -> 'Properties'. Select the 'Sharing' and click 'Share...'
2) Choose 'Everyone', click 'Add' then 'Share'
2) For Windows 7, you will need to turn off password protected sharing (don't do this if you're using your laptop outside of home network). Go to Control Panel -> 'Network and Sharing Center' -> Change advance sharing settings' -> Scroll to the bottom, select 'Turn off password protected sharing' and save.
3) On your Android device, open ES File Explorer and change to 'LAN' view (top left corner button). After that press Menu button -> 'New' -> 'Scan'
4) If everything goes right, you should see your PC name (or IP Address) on the list. If it failed to find your PC, you may need to enter the IP Address of your PC manually by going to Menu -> 'New' -> 'Server', enter the IP Address and then check 'Anonymous' and click OK.
5) Browse to your movies folder and tap on any video, select a video player to play it. Note that some video player might not support streaming, in any case you should install some good player such as MoboPlayer or MX Player.
PS: This is not limited to video only as it works for songs, pdf, docs, anything you could open with your Android device!