I don't know anything about Yahoo or hotmail.
Using Outlook or Outlook Express there is a Tool button on the top bar.
Clicking on it opens a menu with Accounts, clicking on it opens a series of
windows to change the default account. I imagine you have such a tool when
you open the software you use for e-mail.
If you want to make new reduced size files of your existing files and then
cut and paste, it is easy to do.
.. To decrease the size of the file for e-mail, web publishing etc.
Go to this site and download the free Image Resizer. Exe file in one of your
folder.
http://www.microsoft.com/windowsxp/pro/downloads/powertoys.asp
Once in your folder, double click on it to install it.
Once installed, you right click on a photo file (or on a group of selected
photo files).
Click on Resize image on the opening menu.
A window will open, select the size you want.
New files will be added in your folder, same name as original file but with
the word (small) added.
The first time you use it, you may not see Resize image listed on the
opening menu after you right click on the file. If so, do the following:
Click on Run, click on Start and type the following in the textbox:
REGSVR32 SHIMGVW.DLL
and press the Enter key.
Note that there is a space between ...32 and SHI.
This will take a second to run and then Resize image should be listed on
your right click menu.