Outlook 2003 Mail Client Errors

I'm running Office 2003 on Windows XP pro. I keep getting "either there is no default mail client or the current mail client cannot fulfill messaging request. Please run Microsoft Outlook and set as the default mail client" I've checked my Explorer settings and have Outlook as my default mail. I've checked my Outlook settings and checked default mail setting. Did not cure problem. I tried deleting the registry key for Outlook and ran Detect and Repair utility. Has not fixed my problem. I've run Spyware and Virus scans. What ever I try works for a day and then message comes back.What am I missing ?

 

Might work to do a simple toggle.

- change to Outlook Express as default
- reboot
- change back to Outlook as default.

If not, click on start, on run, key in

Code:

sfc /scannow

and OK to let the system file checker replace any damaged or missing system files you might have.