For vector plots - I assume you are trying to draw a 2d field of vectors of variable lengths. How much work are you prepare to put in? If you make an xy plot, but have blank rows in the series (assuming they are columns), then the lines will be separated.
If you need to add arrow heads then a little geometry is required to draw them, using the same trick.
You can do surface and contour plots directly, so long as your data is in a 2d matrix of heights. If you have a list of x,y points, or x,y,z values, then you need to turn it into a 2d matrix first. There are various ways, depending on your data.
You might want to look at Scilab, it is free, powerful, and ported to Windows. Google will find it, although i've also given the web adress in another post here.
Cheers
Greg Locock