Excel 2007 : Excel 2000 File not opening Properly in Excel 2007

Hi

Guys I have a client who has quite a large Excel file that was created in Excel 2000 (19mb Large) The file opens up perfectly with all calculations showing in Excel 2000 but when I try to open it in 2007 the calculations don't show correct and the fields are showing up as #NAME. The Spreadsheet contains multiple worksheets.

You may not have a required add-in loaded (e.g., the Analysis Toolpak), or macros may be disabled. Functions that have a #NAME! error as an argument will propagate the error, so you need to find the first formula that generates it -- a little sleuthing with the auditing toolbar should do.

Just to give a little update , the majority of the fields in questions are showing ### and when I hover the mouse over these fields it says #VALUE! an eg of the formula is "=FIXED(G88,0,TRUE)&" '""

=CALCULATIONS!J5 is another formular that is showing incorrectly.

Is there some kind of compatibility issue between older version of Excel and Excel 2007? Like I said it works flawlessly in 2003 and below.