If you need to get something done by constantly feel bombarded by distractions around your computer, there's no need to block programs from running — you can just shut down your taskbar so you can't reach them.
If distraction-free writing tools just aren't doing it for you, you can make nearly any app distraction-free just by closing explorer.exe. Reader Я Ξ √ Ω L U T ↑ ☼ N $ explains:
Gotta do something that doesn't require Firefox or Chrome, but keep getting distracted by the interwebs? Close explorer.exe from the Process Manager, and keep only the window you need open. I was writing something long in Word recently, and I would continuously go back to Firefox to check my email or the news even though I didn't need to. Closing explorer.exe prevented me from going anywhere until I opened explorer again.
It's a very simple way to rid yourself of potential distractions. Sadly, this doesn't seem to work on a Mac, which relaunches the Finder and Dock every time you quit them (though you could hide the Dock from System Preferences — just having it out of sight may help keep you from distractions).