Howdy:
Couple things to try.. BTW, is this with Outlook or Outlook Express??
As per Microsoft..
1. Click Start, point to Find, and then click Files or Folders.
2. In the Named box, type folders.dbx.
3. In the Look In box, click your primary hard disk (usually drive C), and then click Find Now.
4. Right-click the Folders.dbx file, and then click Rename.
5. Type folders.old, and then click OK.
6. Start Outlook Express. This creates a new Folders.dbx file automatically.
or this one..
1. Click Start, point to Find, and then click Files or Folders.
2. In the Named box, type Sent Items.dbx.
3. In the Look In box, click your primary hard disk (usually drive C), and then click Find Now.
4. Right-click the Sent Items.dbx file, and then click Rename.
5. Type Sent Items.old, and then click OK.
6. Restart Outlook Express. This action automatically creates a new Sent Items.dbx file.
Murray