You'll need some sort of preamplifier between the mic and line-in of
your sound card - line inputs are for powered electronic equipment, with
much higher output levels (keyboards, hifi etc.). A good start would be a
small mic mixer, almost any commercial mixer is likely to be better than the
built-in mic preamp in your sound card! There are a couple of exceptions,
but I guess you're new to recording and using the standard PC hardware?
(The engineer formerly known as Homeless)