I suggest that you might find a short list by doing a Google search for "rugged PC" (leaving off the quotes). The first item it returned allowed one to click on "Laptops", which then gave a discussion paragraph or two - and a list of rugged PCs in a sidebar down the right of the screen.
Even though your needs seem to be covered by ordinary Microsoft Office software, I'd think twice about Vista this early in its life. It may be hard/impossible to avoid, however. Dell and HP still sell some models with XP, but this statement is neither an endorsement nor damnation of those makes.
Budget some money for an external hard drive for backups to be left "home" when you travel, perhaps in a safe.
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A month ago I was in the San Antonio, Texas, airport and our departing plane couldn't get departure clearance for a number of hours due to weather at the destination. Fortunately they didn't board us until clearance was received. I got talking to a fellow who traveled around the USA every week. He said he bought two PCs at a time to have a duplicate as a spare since he couldn't be without if one failed. They seemed to be small, light, non-rugged models. He said they survived for two or three years on the road. Remember that a PC is fairly out-of-date in three or four years anyway.
Sorry to be so non-specific and just "theoretical".
seacue