Paper Size Issue on Shared Epson 915 Printer

I have an Epson 915 printer installed on my Vista SP1 PC, print on this
machine is fine. I have another PC using XP professional installed the
shared printer on the Vista PC.
If I try to print use any other paper size except A4 on the XP PC,The
printer will ignore my paper size settings and force set the paper size to
A4,this cause if i insert a 4*6in paper for photo, the printer will output
most part of the photo out of the paper border.I use the Vista PC,then every
thing is fine.

Anyone has idea about this?