what to use for tracking client details

Your CO. has just done a Complete Network Outfit for a new client. How do some of you keep records of all of this information and be able to produce reports for all clients for example with NT4-SP4 and when that’s done add the change that they all have now been updated to SP5 etc etc. Is there a good Service program you know of? OR do you know of a database or Spreadsheet? OR anything? johnw@compresp.com.au