You should get an improvement using a "Proper" microphone but it would be even better if you could run the microphone into a mixer and feed the mixer output into the line input of the PC; the microphone pre-amplifiers in PC soundcards are usually relatively noisy.

An alternative (which I'm thinking about myself)(although I have no actual experience) is to use a condenser microphone that uses a USB connector; Samson do a couple (C01U, G-Track).