Mac OSX 10.3 keeps reverting back to default page size settings when I try to print

I cannot print out anything on a different size paper, other than 8 1/2 x 11--if I try to change the size in "Custom Size" either in MS Word, or in my printer's (HP Photosmart CC4385) greeting card setting, the printer will print as though the paper is letter sized. I have looked at changing the default setting of the Paper Size feature in System Preferences on my IMAC, but the choices are limited to US Letter, A3, A4, A5, Roc 16K, JB5, and the like, whatever the heck those mean. My custom size is 5.5 inches by 4 inches, and I cannot get the printer or the computer to remember that I asked for that size when I set up the "Custom Size" option in ANY software program! How can I fix this problem and make a greeting card?