There are many different formats for saving photos, but the best and most convenient by far is in JPEG.
Using this format you will find that they don't take so long to send via the Internet as perhaps a BitMap (BMP) format. A photo that is saved in BMP format with a size of 901Kb is reduced to only 57 Kb when saved in JPEG. Obviously, this reduces the 'send time' dramatically.
If you have downloaded or transferred any photos to your computer in BMP format and want to change the format to JPEG, it is quite easy.
Open your photo editing software, if you have one installed, and open the photo from wherever you put it. Click on 'File' in the top left-hand corner and select 'Save As'. Then follow the steps 1 - 3 below.
Or if you are using XP, you can do it in the Windows Picture and Fax Viewer. With this, you simply open the photo, click on the small icon at the bottom of the viewer:

Which will open up a window that looks like this:

1. Make sure you are saving it to the location you want it to be saved in.
2. Call it whatever you like.
3. Make sure it is being saved in the JPEG format
Press 'Save' and that is it!