Small digression:
Shrinking images is very easy, for example with the free IrfanView (-> File menu/Batch Conversion). In addition to the pixel dimensions (Set button), you can also specify a target size in kB (Options button) and save all settings in a file, with which you can then process any number of images repeatedly with the same settings (e.g., for a forum). Slight sharpening of the reduced images restores their optimal sharpness. IrfanView also does this automatically if you wish. For different purposes, you can save different profiles and do not have to adjust everything again and again.
It is best to specify a different target directory during conversion so that the original images remain separately preserved in their directory.