It can be frustrating to open an Excel file and be continually asked if you want to update linked information, particularly if you are not sure what information is linked. If you want to get rid of links in a workbook, there are several things to try.
First, choose Edit Links on the Data tab of the ribbon, if the option is available. (It will only be available if Excel recognizes explicit links in the workbook.) From the resulting Links dialog box you cannot delete links, but you can change the links so that they point to the current workbook. When you later save and again open your workbook, Excel will recognize the self-referential links and delete them.
Another way you can find links is to search for either the left bracket ([) or right bracket (]) in your workbook. The brackets are used by Excel when putting together the links to other files. For instance, this is a link to an external file, as it would appear in a cell:
When you find links similar to the above, all you need to do is delete them. Make sure that you search each worksheet in your workbook.
Another place to look for links is in the defined range names maintained by Excel. This is a particularly common place for links if you are working with a workbook that contains worksheets copied or moved from other locations. The defined names, rather than pointing to a cell range in the current workbook, could be pointing to a range in a different workbook. Click the Name Manager tool on the Formulas tab of the ribbon, then step through each defined name, examining the address to which it refers. Delete or change any that refer to other workbooks.
Another place to check is your macros. It is possible to assign macros to graphics in a worksheet. Click on any graphics and see if you get an error. If you do, this is a good indication that the graphic is linked to a macro contained in a different file. If you delete the graphic, or change the macro assignment, the link problem should go away.
Still another possible location for wayward links is in PivotTables. When you create a PivotTable, it can refer to data on a different worksheet in your workbook. If you later move that source worksheet to a different workbook, your PivotTable will be linked to the external data source. The only solution here is to delete the PivotTable, copy the source data back to the current workbook, or move the PivotTable to the external workbook.
Finally, you should check graphs and charts. If you recently moved worksheets out of your current workbook into another workbook, it is possible that charts and graphs remaining in your current workbook now refer to data on a worksheet you moved to another workbook. If this is the case, you will need to either remove the graph or chart, move it to the other workbook, or copy the source data back into the current workbook.