just go to hp...search for software/drivers [http://search.hp.com/gwukeng/query.html?lang=en&qp=&search=&qt=d110a&la=en&hps=Home&hpr=http%3A//www8.hp.com/uk/en/home.html&charset=utf-8&cc=uk&hpn=Home&hpa=http%3A//www.hp.com/country/uk/en/contact_us.html|and you get this]
sounds like you have a blockage in the ink "squirter"(no idea what it should be called, but this is what it does). you should be able to open the hp toolbox from your desktop and run a cartridge cleaner -its basically a one page run which should sort out any ink blockages.