You need style="margin: 0; border: 0; padding: 0; display: block;"
on all images. Also, you can't start colspans with the first row being spanned, Outlook doesn't know how to handle the widths. See here for more information.
Beyond that, you should NEVER use slices to create entire html emails. It is really bad practice, as:
- Images do not load by default in most email clients
- Some spam filters will trigger as the ratio of text to image is too low
- Long download times resulting in poor usability
You'll find a bunch of information on html email best practices here