"LINE IN" Function

I'd like to "rip" some Cassette tracks to my computer, then burn them to CD.  Question I have is, can I use the "Line In" input to do this?  Where can I find information about this input on the Dimension 4300 - the Dell provided "manual" says nothing about it, and I haven't been able to use the Dell Solution Center.

If the Line Input is the viable way, what kind on "line" is useable?  Like many people, I no longer have an audio pre-amplifier.  Can I use the headset output from a cassette player?  Curious.