I don't think you'd be able to fully remove the smell if the laptop is from a
heavy smoker. Especially if you're sensitive to the smell of cigarette smoke.
It's probably better to get another laptop and sell yours to a smoker who
won't mind =)
To improve the situation, buy some isopropyl alcohol (70% solution or less
(more can damage the plastic)) or alcohol pads.
Now apply some of the alcohol on a cloth and clean the whole case carefully,
then remove the keyboard and palmrest and clean everything from the inside.
Use a cotton swab for the fan.
The smell of the alcohol will disappear within minutes - open a window to
avoid getting a headache.
Usually laptops from ebay do have that problem sometimes, it's not related to
free software ;)
The laptops we offer, smell neutral and are perfectly clean, inside and
outside. They don't even smell of plastic (they're well-hung after all).
I think you just had bad luck with your purchase and the company you bought
it from merely a bad day or a cold and they didn't smell it - perhaps they
will contact you and try to resolve that issue, they're active in this forum
as well.