For EPS format, you'd need to paste the image into an image editor (eg Photosop Elements) that can save in that format.

To get the maximum quality for other images in Word, turn off image compression and set the default to 220dpi (I'm not sure where these functions are located in Word 2007). However, Word cannot increase the resolution of an image. If you need better than 180dpi, you'd do best to capture the image at the higher resolution rather than to try to upscale it later on.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]