Minecraft Enhanced is a 256 texture set that is designed to keep the original look and feel and theme of Default minecraft.
How to install Enhanced Resource Pack for Minecraft
In order to use HD texture packs properly (32× and higher) you will need to either patch your Minecraft using MCPatcher or using OptiFine. Optifine is preferred as it includes all of the features of MCPatcher, and greatly increases game speeds and graphics settings. MCPatcher tends to be updated on the same day as Minecraft updates, so use it instead if you are in a hurry.