This is from the following webpage:
http://www.pubassist.com/XPCustom_paper_size.htm
In Windows XP, paper sizes are defined in what are called "forms"
which are independent from the printer drivers.
You can define a new form by selecting the "Printers & Faxes" option o
the "Start" menu. From there, click on the "File" menu at the very top
Select the "Server Properties" option. On the Properties dialog, you'l
see the "Forms" tab. Check the "Creat New Form" box and you will b
able to update the form name and size fields. Click on "Save Form" t
save your new form.
In my testing, I created a new form for a 3 inch high by 4 inch wid
label, and named the form, "1Up Shipping Labels".
Now you can select your custom paper size "form" from the propertie
dialog for your printer driver. The specifics on how to do this varie
with each printer, though I believe the paper size can generally b
found under the "Printing Preferences" option. I set up a printe
driver for an Okidata ML393. I right-clicked on the printer icon an
selected "Printing Preferences". (You can get to "Printing Preferences
from the "Properties" dialog as well.) To get to the custom paper siz
I created, I had to click on the "Advanced" button beneath the "Layout
tab. There I could select the
paper size, and sure enough, my "1Up Shipping Labels" custom form wa
available for selection. This is not the case for all printer drivers
I tried to select the custom page on my Deskjet printer, and found tha
it wasn't available. Apparently, the driver has the intelligence t
know what paper sizes won't work!
Sorry for the late reply but I just ran into the same situation a fe
days ago and just found the answer myself
