There is a simple tool that Microsoft provides for free where you can easily resize multiple images at once. Not only can it reduce your pixel size to 1024x768 or smaller, but by doing so, it greatly reduces the file size as well. I use this feature all the time when I email pictures.
My camera takes pictures at a resolution of 2816x2112 and the file size is in the 3mb range as well. Using the tool from Microsoft, I can make a copy and reduce it to 1024x768 with a file size around 150kb while keeping the high res image as well.
The tool can be found here (this is a direct link to the download from Microsoft's website):
http://download.microsoft.com/download/whistler/Install/2/WXP/EN-US/ImageResizerPowertoySetup.exe
After it's downloaded and installed, you can find it by simply right-clicking on the picture you want to resize and click 'resize pictures' to get to the image resizing screen. To do multiple pictures at once, just click and drag to highlight all the pictures you want to resize and then right-click one of the highlighted pictures.
This is a very simple and easy to use tool. If you decide to use it and have further questions, feel free to ask!