Help with .ctb and pc3, HP Designjet 750c

Hello there:
I know some autocad and my co-workers almost none.
We had an old computer with Windows 98, Autocad Lt 2000 and a HP 750c
Plotter that used to work fine. We just got a new computer (XP) and upgraded to Autocad Lt 2004. We installed the plotter using the driver on the Autocad cd as suggested, but when we try to plot the drawings, it comes very light on color, and not the right paper, and the ploter tell us "the media is too small". I believe it could be pen thickness or configuration.I was told to go to the old computer and get the pc3 and ctb file. I did but I don't know how to enter them into Autocad. I don't see that option. THere was an option to enter a pc2 from Autocad 14 but that is not my case. I have registered in a school to learn more Autocad but so far we haven't got there yet. Thank you for your help.
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