Paper size not found - added plotters

Draftsman wants to plot a dwg. He hits plot, and gets the following dialogue box:

Paper Size not found
The plotter configuration is not set up to support the current layout's paper size.
AutoCAD can attempt to use the custom paper size or use the printer's default size.

Choose: Use default paper size Custom 5: 38.75 x 30 in
or Use custom paper size (36.00 x 24.00 inches)

He selects second option (36.00 x 24.00 inches) which is what he normally uses, and is taken to the plot dialogue box. However - Instead of the default plotter selected as the plot device, it lists a NEW plotter - such as

HP 1050C OurPlot

Next time he tries to plot, he goes through the same things, only the plotter listed for the next dwg is

HP 1050C OurPlotaa

Each successive time a dwg is plotted, the program is adding another plotter - a, aa, aaa, aaaa, etc.

Has anyone seen this before? Sound familiar? I'm not even sure what terms or phrases to use to search for possible solutions.
C~

 

Ack! Additional info.

ACAD 2004
Win XP SP1
What else?

This only started happening today, although he's been out of the office of late. This is the first day he's mentioned it to me.

 

I see this quite often, I typically click on "Use printer default" and then
select the paper size you want.

 

Thanks, but he doesn't want to use the printer default - he says he has the plotter and plot styles set up the way he wants them.

And this still doesn't address why ghost-plotters are being added each time

Plottera
Plotteraa
Plotteraaa
Plotteraaaa
??

Still no joy.
C~