If there's still some warranty left, start with about 50% of what an equivalent new model would cost -- or about $250, since a new base Inspiron 17 is about $500.  You'll probably get more like 35-40% or between $175-200 for it.

Look on eBay and you'll get a good idea.

And if you try selling on Craigslist, you'll find a lot of bottomfishers aka lowballers.

An used laptop is like a used car, once it is driven off the lot, it loses 1/2 value if not more.

Good luck