Software

To All: Please be advised that at x:xx time we are planning to upgrade all users to the newest browser of Internet Explorer.

I would also include if there is going to be any down time associated with the upgrade, which I doubt since it's only IE 7.

I would inform the users of the scope of the change (in your case upgrade to IE 7). I would tell them the date and time of the change including any downtime. I would send the notice out with adequate lead time to give them a chance to prepare for the change (maybe 2 weeks notice). I also typically determine if any training is required prior to the change (a brief demo for IE7 should suffice depending on the current version). In the case of an upgrade, review all the new features.

For a more striking effect, use a mail merge with some personalized information in the body of the notice.

Lastly, I?d send out a reminder shortly before the implementation date as some users are sure to forget.

Make the Subject line something that will peak their interest. Does no good to send a heads up if all you get is(opened. deleted.) in your sent items properties.