I have two linked excel files, enquiry.xls and data.xls

The enquiry.xls is with the vlookup formula to lookup the data in data.xls.
It works OK, however, when the data in data.xls upto row 5346, the lookup in
enquriy.xls returns with the error message stating that the memory is not
enough. There are 13 column (i.e. col A to M) in data.xls, and my PC is
running Windows XP SP2, Office 2000 (Chinese) and with 1GB ram on board.

What is the problem caused the error and how to correct it ?

Thanks,