Ok, so after getting the oil and filter changed, I'm still getting some
valve (or other mechanical noise) when I first start my 99 Altima.  The old
filter was a Carquest generic one, and I now have a Nissan one on, although
it's white with red lettering instead of blue.  Anyway, I was hoping someone
could tell me not to worry about the sound so I could stop being so paranoid
about it :)

I'm just trying to think of what might be wrong, if anything, that would
make that sound..  Does the 99 have hydraulic lifters that might be taking a
couple of seconds to get filled up?  Once the tapping stops, it sounds fine,
and doesn't make any other strange sounds.

The really odd thing is that it happens first thing in the morning, and when
I leave work at the end of the day, but if I go out at noon, it's almost
inaudible, but WILL be heard again at 5pm.. this has happened 3 or 4 times
so far since I've been paying attention to it.  It sits for 3 1/2 hours
before lunch, and for another 3 1/2 hours after, so it's not simply because
it sits longer in the afternoon.

Any thoughts?  Should I take it to the dealer, or is it normal and should I
stop asking about it? :)  What worries me is that I've never heard this
kinds of tapping from my 94 except when it's been below -10 degrees C
outside.

I'd probably have to leave it overnight for them to hear it, so it'd be a
bit of a hassle, but I suppose worth it for some piece of mind or at least
to get it fixed.