The steps are as follows :
Excel 2007 is the only compatible version for Excel Services Configuration with MOSS 2007.
Open your sharepoint portal -> Site Actions -> Create -> New Doc Library -> Give Title & Desc -> Select Document Template as Office Excel Spreadsheet
Open Excel Workbook -> File -> Publish -> My Network Places -> Select your Excel Library -> Chk open in excel services -> Excel Services Options -> Select Sheet -> Items in Workbook -> Select Chart -> It gives a permission error
Open Central Admin -> Shared Services Admin -> services on server -> start Excel Calculatio Services -> Shared Services -> Trusted File Locations -> Add T. F. Loc -> Add Library Location (URL) -> Select Children Trusted -> Select Trusted data connection libraries & embedded
Open the page on your portal where you wish to host your Excel Charts -> Edit Page -> Add New Web Part -> Select Excel Web Access Webpart (in business webparts) -> Open tool pane -> Select Workbook