What is the resolution of the graphics files? Other than dimensions (height x width), one of the biggest contributors to a graphic's file size is resolution.
The resolution you choose for the graphics however is dependent on what you are going to do with the file. If it to be printed in reasonable quality (i.e. not visibly pixelated) on a desktop printer (inkjet or laser) then 150-200 dpi is probably fine. Hoever, if you are using GIFs and JPGs then resolution is not nearly as significant. Unless the Word doc is for display on the web. Then 72 dpi is all the resolution you need.
To reduce the size of a JPG file, open it in Photoshop, and use a lower quality factor when saving i.e. more compression. For a GIF, you can reduce the number of colours to reduce file size.
But if you have a lot of graphics in a Word file, then there is no way of avoiding a large file size. Graphics require a lot of bytes to describe their content.