If you want to disable it for ALL of the reports in your system, you may be able to modify the .csp page that displays the reports. I don't have a copy of CE 10 available so I can't tell you which specific file.
Another, probably simpler, option might be to update your installation and remove the export files for everything except PDF.
Either way, this change will apply to everything you publish to CE. As far as I know, there is no way to limit this to specific reports.
-Dell
A computer only does what you actually told it to do - not what you thought you told it to do.