Hi Bryan,
(And good morning, Ian),
"Duplex printer" is just another term for a printer supporting printing to both sides of a single sheet of paper in a single operation.
According to the HP website, your HP 7100 series printer does do 2-sided printing, so you should be good to go once you've located the settings described by Yellowbox.
One note on those settings, though: Don't take them literally, Set up the 'low ink use' test card as described by Yellowbox, set the page orientation to landscape, and the 'binding' setting to match the settings in his example, then Print.
If all turns out fine (and I expect it will, as Yellowbox notes it was tested using his printer), you have the right setting for your printer.
If not, change only the 'binding edge' setting and print again.
You may want to Save the 'correct' settings as a 'vertical 1 fold card' preset.
To do so, Click on the control at the right end of the Presets box to open the list, then select Save current settings as Preset" near the bottom of the list.
Regarding the Birthday Card template:
"on the flip one (shows gift boxes) I can't get the print to come on top page before you flip open."
Page 1 of this template is the outside of the folded card. The 'back' of the card is the 'empty' half (the text box there is intended to be removed before printing) is the back, and the bottom half is the front of the folded card.
The second page of the template is the inside of the card. The bottom half, containing the text box, is the part seen when the card is removed from the envelope and the front page lifted.
Additional text (or graphics) can be placed on the top half of both pages.
To appear in the correct orientation on the closed card, the text box and images on the outside top (card back) must be rotated 180 degrees.
Text or images on the top half of the inside page will appear in the same orientation on the open card as they do on the template.
Regards,
Barry
PS: You mentioned that "2 sided does not work. " Do you mean your printer cannot do two sided printing, or that it does print on both sides of the sheet, but the resulting print is oriented incorrectly? If the latter, the posts to date should solve your issue; if the latter, let us know—there are ways of doing 2 sided printing using printers that do not support that feature.
B.