>Pls note that when i change the value manually, after each restart it sets it back to the old value..
>

If the registry chages is being saved properly, there's something resetting it; I'd look to see if there's something either starting up Eudora, or that something like a roaming hive (a special type of file that carries information about the HKEY_CURRENT_USER that can be set up in NT) is being used and not updated properly. It may be setup in any number of ways, like through a system policy defined to the system. If a registry key change is saved, it should not revert on a reboot, so some other mechanism is working here.

If this is NT, or in an NT domain, there may be security restrictions preventing the registry key from being saved. An unprivleged user id may not be allowed to change settings. Again, this is well beyond the issue, and impossible to diagnose without a detailed examination of the system. If this is a network environment, especially one where NT and system policies are involved, it's probably time to get a network administrator or someone with more of an idea about how the network is set up to look at it.

>Outlook gives this option of making it as a default mail client but only at the time of installation...
>
>Pls advs. ur comments...

I have no idea, since I can make manual changes to my registry under both NT and Win9x and the change 'sticks'.