It depends how and where you sell it. Try places like ebay and then it may sell but with the costs of shipping and ebay fees.
You can use Gumtree, list it for around £60-80 depending on condition, if you're lucky you might get more but it depends. I have found dual core PCs of similar specification selling for less.
Also it depends which COA it has, Windows 7+ then you're fine, but if it's Vista or XP - or somehow even older - then you will be looking at a bit less.