Another thought.
You can open the picture in "Paint" and on one of the drop-down menus it says "Attributes". This will give you the pixel dimensions of the picture.
When you try to post, do you get an error message that says "The image is too large, please post image that is 500x600 or less" (or something like that)?
Once opened in paint, you can reduce the size by a selectable percentage-click on "Image" then "Stretch/Skew" and then type in the percentage number you want to reduce it to in both the vertical and horizontal boxes.
Also note that you can select an area of the picture and save just that area. Example-You have a nice riding shot of yourself but you are small in the picture and there is a lot of excess scenery that you want to trim away.
Just play around with it, that's how I learned myself how to do it!
BTW-Save the pics as .jpeg's, not .gif's or .bmp's! Those file types are typically 6-10 times larger than a .jpeg. Use the drop-down window for "Save as Type File" when you click "Save As" after doctoring your image.
You can Email me direct if you have any questions. Good luck!