There's a couple of things you can do besides upping your ISO.
1) Get a faster lens(Smaller f/number). That allows more light in, so you can use a faster shutter speed. This is the expensive route, usually. Except for the 50mm f/1.8. Very good lens for the money. You'll fall in love with it.
2) Use a flash that you can bounce off the walls or ceiling. For a Nikon this would be SB400, SB600, or SB800. I'm not certain about the D40x, but you should be able to get at least 1/200th if you go into manual mode or shutter priority mode.
By the way. I'm not an expert, so others may come along with better ideas for ya.
