The main factors here are the size of the file in bytes (not its dimensions
or dpi), and the attachment size limit on both e-mail accounts. It seems
unlikely that your laptop has anything to do with it. My guess is the
attachment size limit on the recipient's e-mail account is much smaller than
the image you're sending.

I am trying to send photo attachments to emails. The recipients say the
attachment arrives with this message: "The sender sent this message in 7
parts because it was too large to send as a single message. The raw source
of each part can be seen by selecting the View->Message->Raw Source menu
item."
The photos are 600 by 450 proportional range and 72 dpi. I size them at no
more than 8" wide. They have been saved in Photoshop Elements as .jpg files.
I never had this problem until I got this new laptop with Vista on it. Can
anyone help?

please visit www.microsoft.com

Go to Tools, Accounts, select your mail account, Properties, Advanced,
uncheck "Break apart messages larger than..."

I am trying to send photo attachments to emails. The recipients say the attachment arrives with this message: "The sender sent
this message in 7 parts because it was too large to send as a single message. The raw source of each part can be seen by selecting
the View->Message->Raw Source menu item."
The photos are 600 by 450 proportional range and 72 dpi. I size them at no more than 8" wide. They have been saved in Photoshop
Elements as .jpg files.  I never had this problem until I got this new laptop with Vista on it. Can anyone help?