|The simplest way, though it's a bit of a 'sledgehammer approach' is to delete the inbox and let OE create a new one.|
First, create a new folder (not in the inbox) and save any messages you want from the inbox into it. Next, click on 'Tools>Options>Maintenance tab.>store folder', copy its location and then paste it into 'Start/run' and click ok - this should open a window with a load of .dbx files. Make sure OE is closed and then delete the 'inbox.dbx' file (you can rename it to 'inbox.old' if you don't like the idea of deleting it, just in case of problems). Re-open OE and you will have a new, empty inbox - you can then copy any previously saved mails back in.
"I've always been mad, I know I've been mad, like the most of us..." Pink Floyd