Rows missing while exporting to Excel

One of my client's system environment is SAP 2007A PL:42, Excel 2000

While exporting the query results to excel without sorting, its exporting the whole records (nearly 13000 lines). If I sort with Column-A, its exporting nearly 12500 records only. Even strange is that, if I sort with Column-B, its exporting only 12000 records.

In all sorts, the SAP is displaying the whole 13000 records, but problem is in Excel export only.

Regards,

Bala