Google Picasa is a good, free download editing program. You can tidy up your pictures and use the 'Export' function to resize pictures for your e-mail and ebay use.
Without downloading any new software, use Windows Paint.
Easiest is probably-------------------
Open your picture
Right click on it
Select 'open with' and left click 'Paint'
Use the resize option, top left.
Save the picture in another file, (using 'save as' ) resized, and attach this to your e-mail.
When you exit Paint it will ask 'save changes?', select 'no', and your original picture will be unchanged.
This is on Win 7, other versions may vary slightly.
