Sorting is very slow in Excel 2002 and 2003

I have a user who used to have Office 2000 who was recently upgraded to
2003. She has a 20MB Excel Spreadsheet that she works with daily. When she
had Excel 2000 she could sort one column in 6 seconds. Now with Excel 2003
it takes 4 minutes to do the exact sorting function.

She has a 996mhz processor and 256MB of ram, I upgraded her to 512 MB of
ram, same results. But a lowly 350 mhz processor with 256 MB of ram that has
Excel 2000 opens the same spreadsheet in 6 seconds. This tells me it is not
a hardware issue.

I have tested this same spreadsheet on various PC's all with the same
results on Excel 2000 it sorts in 6 seconds on Excel 2002 or later, it takes
4 minutes to sort.

Any idea's why this is happening or possible solutions?

Thanks,
Lee S.