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If there is an error loading the DLL there is a fault either with the Excel application or the DLL. Either of these might have become corrupt, perhaps under the influence of a virus or by some less ominous process.
- To eliminate the virus, if any, run a good virus scan.
- To repair Excel run Excel's own repair feature.
From the Control Panel select Programs > Uninstall and Change.
Select Office (or Excel), double-click and choose Change.
Choose "Repair". You will require access to the original installation software.
- There is a very good chance that the repair process will actually also include repair of the DLL. If the error persists after repairing Excel obtain a good copy of the file in question and replace it on your computer. You can get the file from a colleague or you can download it from the web. Make sure that you place the file in the correct directory.
Note that repair of Excel is a separate process from eliminating a virus. Killing the virus - if one exists - will not undo the damage it already did. And repairing Excel will not prevent the virus - if one exists - from damaging it again.