MrDEB,
Just because the software lets you use 8 mil track widths doesn't mean it's a good idea. 8 mil is pushing the limits of what a cheap fab house can do. If you're laying out a high density surface mount board, you may need to use 8 mil traces, but unless you absolutely need such thin traces for clearance, it's prudent to use larger trace widths.
Your board is not that dense. There's plenty of room for 16 mil or larger traces, and for power and ground, I'd suggest even larger.