Firstly: The initial "V" of Hallow/Corruption/Crimson. Most notably, notice the picture:  <strike>IIRC, the V is "centered" on where you killed the Wall. So move the wall left, or right and follow it at an angle to your house. I may be wrong on that part.</strike> [this](http://terraria.gamepedia.com/Hardmode) states that `Immediately, two diagonal stripes of the new biomes generate, replacing large sections of the World in a "V" pattern that extends from the center of The Underworld all the way to the surface.` Things might have changed with 1.3, but most likely your house is near one of the "Sides" of the V. Secondly: When you "smash" an alter you create small pockets of one or the other: > Upon smashing a Demon/Crimson altar with the Pwnhammer (Or more powerful tools later on in the game), there is a chance of a single block of your world turning Hallowed or Corrupt/Crimson in a random place, which given enough time, will spread to form new, large areas to deal with. So the basic gist is that your house is in a "bad"/"unlucky" place. The biomes can spread - either with time or smashed altars+time - but if your house was "immediately" in a spot, it's all location. You can remove the corruption, the easiest method is a clementator - which spray changes an area into a biome of choice. http://terraria.gamepedia.com/Clentaminator > The Clentaminator is the fastest means of spreading Hallow, Corruption, Crimson, and Mushroom Biome, or purifying biomes of Hallow, Corruption, or Crimson. You can also clear a surrounding area - 3 blocks to stop the spread - and turn your home area into something like Jungle or Mushroom Biomes. Also, check your backup folder for a save from before the switch to hardmode for a "hard" reset back. > C:\Users\<User>\Documents\My Games\Terraria Lastly, if desperate and map dependent, you can try to use [TEdit](http://www.terrariaonline.com/threads/tedit-terraria-map-editor.35394/) - Its not been updated for 1.3 yet, but there is a chance that your world was made before. (backup world before experimenting irregardless) Links related: http://terraria.gamepedia.com/Guide:Containing_the_Hallow/Corruption http://terraria.gamepedia.com/Hardmode http://terraria.gamepedia.com/Clentaminator