Line In Doesn't Appear Anymore

I used WMM for months, sending audio through line in and saving it as a wma
file. I even wrote myself a word document listing the steps I needed to take
to do the recording. Now when I start it up and try to record (via the
narration recording feature) it doesn't list line in as a recording option on
the appropriate sound device. I have no doubt I'm doing the recording
process same as I always did with all the same choices made along the way. I
can record via line in on voice recorder, so it seems the device is
physically set up fine too. Is there any reason Line In wouldn't appear?
And more importantly, can this be fixed?