Outlook 2003 Issue

This should help:
The Locate Link Browser dialog box appears when you open a Web link in an e-mail message in Outlook 2003

To resolve this problem change the registered file type for the URL:HyperText Transfer Protocol file type to use Internet Explorer. To do this, follow these steps:

1. On the desktop, double-click My Computer.
2. On the Tools menu, click Folder Options, and then click the File Types tab.
3. In the Registered File Types list, click URL:HyperText Transfer Protocol, click Advanced, and then click Edit.
4. In the Actions box, type open.
5. In the Application used to perform action box, locate Internet Explorer (Iexplore.exe), and then click Open.
6. In the Application box, type IExplore, and then click OK.

Ok, try this one:
OL2000: "Locate Link Browser" Message When You Click a MailTo Link

To resolve this problem, click to clear the Use DDE check box:

To Deselect DDE

1. Double-click My Computer.
2. On the View menu, click Folder Options.
3. On the File Types tab, click URL:MailTo Protocol in the Registered File Types list, and then click Edit.
4. In the Actions box, click open, and then click Edit.
5. Click to clear the Use DDE check box, and then click OK
6. Click Close, and then click Close.