For under 400$ you might wanna check around on Ebay and do a little research into what components are the best for you and what you need.
I'm sure you could find something,I mean I found my Wacom Bamboo tablet for 50$ and it's brand new/works fine.
There's not really any good laptops under $400, unless you don't mind getting something used/refurbished. As SM said, you could try Ebay, or look at some local pawn shops. They occasionally have some decent ones for cheap.
What Chrysocyon has linked for you is the best one. I had that exact processor I used to have and its is a very strong quad core processor with a nice gpu built into it. You will be able to do a lot with it.
Email LaptopExperience http://www.laptopexperience.com/ . He sells used and refurbished off lease business laptops. I got my engineering laptop from him last year and it has been great. I use it for running analyses and 3d solid modeling, both of which are more hardware intensive than most art programs. Best of all the computers come 100% ready to go and almost all of them are under $400. 1-2 day shipping also.