Unfortunately boosting the Mic input means not only amplifying what it hears but also the noise floor.
That is to say that a byproduct of amplifying the input is a noisier recording.
This is especially true when you consider that you are using an inexpensive CODEC to perform the amplification.
If this is something you enjoy and think you will be doing for a while, it would probably make sense to invest into a bit of gear.
As an immediate solution I would recommend looking into a dedicated microphone preamp.
In function a preamp will work similar to your sound CODEC's boost function in that it amplifies the microphone signal.
As you have dedicated hardware for performing the amplification however the sound quality will be greatly increased.
Amazon has Quite a Selection
, unfortunately I am none to familiar with mic preamps and would not be able to recommend a specific model.
As future upgrades, a dedicated sound card and higher quality microphone would make good investments.