Its probably because you have not resized after uploading from the camera - they are always massive in size - I hate it!
Free to use is
http://imageshack.us/ pick and tick the resize option!
Or grab an account at
www.photobucket.com upload pics & press edit to see rezie options although with these if your picture is large from camera upload they tend to take ages unless you have reduced size in paint or simular - I use paint personally that is aready provided on your PC install.