printing a5 in hp4000tn - "tray 1 load preprinted a5"

[i_love_hp_error_codes]

hi - am trying to print to A5 sized paper in tray 3. Have downloaded the latest driver from hp. have set up tray 3 to be a5 in the printing preferences from the general tab and also in hte advanced tab under printing defaults - paper have set tray 3 as a5. when i try to print to a5 it comes up and says

"tray 1 load letterhead a5" or "tray 1 load preprinted a5"

help!

os is windows xp sp2

[AprinterTek]

When Manual Feed is selected, if TRAY 1 MODE=FIRST the printer
automatically prints (if paper is in the tray). If TRAY 1 MODE=CASSETTE
the printer prompts to load Tray 1 whether or not Tray 1 is loaded.
This enables you to load different paper if necessary. Press [Go] to
print from Tray 1.

To print by type and size, it might be necessary to unload or close
Tray 1, or set Manual Feed to *OFF from the Paper Handling Menu
in the printer’s control panel.

hope this helps

[Strider]

You must choose the same paper type in the program and for the cassette as well as the size.If tray 3 is set to a5 and regular paper,then if you choose a5 and letterhead in the program,then it will prompt you to "load a5 letterhead in tray 1".