Sounds as though you've saved the workspace at some point.
See the Excel help for deleting a document workspace:
Delete a Document Workspace
Deleting a Document Workspace site removes all the data in the Document
Workspace and deletes the document library in the Document Workspace,
including all the documents stored there.
Notes
a.. You must be an administrator of a Document Workspace to delete it.
b.. Deleting the Document Workspace does not delete your own copy of
documents that you are storing on your computer.
Do one of the following:
Use the Shared Workspace task pane
a.. In the Shared Workspace task pane, click the title of the Document
Workspace, and then click Delete Workspace.
Use a Web browser
1.. In the Web browser, open the Document Workspace site.
2.. On the top link bar, click Site Settings.
3.. Under Administration, click Go to Site Administration.
4.. Under Management and Statistics, click Delete this site, and then
click Delete.
Regards
Trevor