What you need to do is open your old data file using File->Open and then select "Load last file during startup" checkbox under Tools->Options if you want to have the file opened automatically each time you start AceMoney. AceMoney data files have .mmw extention, if you don't remember a location of the file, you can find it by searching (Start->Search for files or folders and enter *.amj (or *.mmw) as a file name).