My jungle, corruption, and hallowed biomes all spawned in the same place, so my world is only 1% Hallowed and it's not increasing, however I need a hallowed Biome so I can get the Storm Bow, any solutions?
The Hallow and Corruption Biomes can spread by grass and stone proximity. So, in addition to the Clentaminator mentioned above, if you collect the pearlstone and place it near regular stone in another area, it will start to convert and spread the regular stone to pearlstone. For corruption, it works the same way but with ebonstone. I think the pearlstone will also convert regular grass to hallowed grass.
This will eventually reach down into the underground, but you could help it by digging a channel down.
Also, most biomes in Terraria are based on the surrounding blocks. So, you can create an artificial hallow biome by simply placing a minimum number of blocks (I think it's 80) of the correct type. e.g. Plant jungle grass seeds on a pile of mud, and when it spreads far enough you'll have a jungle biome.