pixel size for photo prints.

My C80 Epson printer is a little lacking in quality where
I print photos that I have scanned on a HP ScanJet 5100C
and tried to improve with PSP 7.  I like to
take a floppy in .jpg format to a local one hour photo
developer for prints. Usually, I go to Wal-Mart for this,
therefore their operators only insert the floppy and
push a couple of buttons in a gray box, which I understand where I
only pay  twenty cent per print.

My problem is that I do not know the pixel size or optimization
standards on the scanner or PSP 7 when processing forcopying
to floppy disk for obtain standard 6" X 4" prints. As a result
I received prints that are truncated or blancked on portions
of the print in addition to a lack of clarity and contrast.

Would someone be so kind as to suggest a pixel size in
length and width that might help the sizing problem? Any 
other tip you might give me including the URL of a tutorial
would be appreciated.

I am still with Windows 95 on a 200 MHZ Gateway if this
has any bearing.

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