How to open Excel 2007 spreadsheets in different windows on Windows Vista and Windows XP
Step 1: Open Excel 2007
Step 2: Open Excel Options (from the big office button on top left)
Step 3: Go in Advanced (in Excel Options window)
Step 4: Then scroll down to see "Display" option
Step 5: Tick "Show all windows in the Taskbar" option
Step 6: Click "Ok" button
And you are done.