also m8
have you installed / uninstalled and new programs recently ???
Uninstalling IE6 will cause problem with .eml file types
Re-register .eml file type with OE
RESOLUTION
To resolve this behavior, either run the Msimn executable file with the /reg option to force Outlook Express to re-register its file types, or re-register the .eml file type in My Computer.
To run the Msimn executable file with the /reg option:
Quit Outlook Express.
Click Start, and then click Run.
In the Open box, type msimn /reg, and then click OK.
Manually add .eml file types to OE
Outlook Express will not open .eml attachments
After uninstalling IE6
You will need to add the "associations" to .eml attachments manually:
Open My Computer (or Explorer) open the View tab and open the (Folder) Options then open the File Types tab, scroll the window down to Outlook Express Mail Message (it will usually be below the My Documents) if it is there click Edit (if it is not there click New Type) it needs to have the following settings
Description of type: Outlook Express Mail Message
Associated extension: eml
Content_Type (MIME): message/rfc822
In the Actions: window select New / Action open
Application used to perform action: "C:\Program Files\OUTLOOK EXPRESS/msimn.exe" /eml:%1
Note the space after msimn.exe" and type the /eml:%1 exactly. If Outlook Express is not located in the Program Files folder you will get a cannot find message, if the line is not typed exacly as it is above you will get a cannot find message.
Select save (or OK) then save and OK (if asked) and any other save or OK messages you recieve.
No need to reboot it should work properly now.
also, do you run anti-virus software ????
(the nimda virus is linked with .eml file types !)