I don't know if this might help you, but if you want to get a pc with a microphone, you can always get something like
this
or
this
these are very practical solutions to your needs, you find this stuff all over eBAY just search for MD microphones, these were made for mini-disc recorders but will work just like any other microphone

.
I am actually thinking of getting the first one for my Thinkpad R50e.
EDIT :
Originally posted by: DaWhim
I know all ibm thinkpad has a microphone. what else?
Oops I didn't read you post carefully I thought you wanted a laptop with a mic and I suggested those accessories, and to answer your question, not all IBM Thinkpads have a microphone, my R50e doesn't have one. So maybe all the T,X & Z series ones, and possibly the R52 one's too.
I used to have a Compaq E 500 and as one member before me said it is located in a good location on the bottom right corner of the LCD.