plotting a graph in excel 2007/win xp gives run time error

i have developed a module in visual studio 2010 using vb.net which transfers data to an excel sheet.this program when deployed on win7/excel 2010,win7/excel2003 works ok

it also works ok on win xp/excel 2007 if you log in as adminstrator. but gives error when executing chart.add(x,y,z,a)