Prior to spending on a 'resetter' you could try 'SCC Service Utility 4.30' ( see August 2008 edition of PC Advisor page 138 ).
If your printer, like mine, is not on the list then try the :-
JET TEC Inkjet Ink Cartridge Chip Ink Level Resetter
They are also available from other outlets ... check to see if your printer is covered by the spec !!!!!!!