Photo paper sizes on Epson Stylus Photo 890

I've just acquired one of these and I've been trying out it's photo printing
abilities.

The quality is excellent, but I've been having trouble with fitting the
image on the paper. If I choose 4 x 6 then I get three white borders but the
image extends over one long side by around half an inch. It does this
whether I select fit to frame or crop (I'm using PhotoQuicker). If I select
150 x 100 paper size then it fits perfectly but will only do borderless.

Is this a driver problem or just stupidity on my part?

Thanks,

Mike