I'm not an expert on laptops however I personally would get a Toshiba if I was going to get one. They are sturdy, well built and very reliable.
I would recommend that as its getting used for business that you get an external hard drive as a back up for your business files and perhaps a program such as Acronis Drive Image which will back up everything.
Even the best of computers fail and if you're talking about business then its foolish to have no backup.
As an example of a nice Toshiba click here might be overkill for you but its got XP on it rather than Vista so would run happily on the 512mb ram. There are cheaper ones, PC World are doing one for less than £400 as an example.
Any laptop will really do what you are asking but personally I like Toshibas, two of my friends have them and use them for their business and so far they have been 100% reliable.