My fave is IrfanView:
http://www.irfanview.com/
Download it, keep it on desktop or in programs.
-When you use it, simply open it, peruse your pics docs,
select the pic, "open that pic" in Irfanview.
-Hit Control R and up pops a screen: reduce pic to 800x600 or
480x640 or, smaller, apply that...
-hit Control S to save: adjust "quality" in the lil' box, eg 90% or so, rename file if you want
-hit ok and it's saved.
-Then using the Manage Attachments in the Advanced Post area,
pull up that pic, using Jpeg/gif code,not "all files"
-upload in that Att. Management box, close,
and post.
It reads about 10X times more complex than it is; sort of
like describing how to drive a stick shift.
Easy stuff, even for this ol'bastard.
GL,mD