Well this is another reason why I use two options rather then one for imaging. If one proves to be a problem I will use the image created by the other. To date I haven't run into any bad despite the numerous images over the last 2+ yrrs. for both pre and retail 7 installs.

As for data I typically download one program 2 or 3 times and each goes to a separate drive especially now with the next version's RC equivalent on. That serves to back up as you go along while I could still download again at another time following a clean install or reimage at any time.

The things included in the first images will be those things that you would want on all the time and not a bunch of temp files. Once you have all the basics on that's the ideal time for creating an image or two.