You can only control the behavior of the notifications. As you probably
know, that is done by highlighting an item and adjusting its behavior with
the corresponding drop down menu on the right of the item. Some items in
the notification area are startup icons and whether or not you have to edit
the registry to remove it depends on the particular startup program.
To view which ones you can remove by deleting from the Startup folder and
which must be edited in the registry, go to Start>Run and type
msconfig
Select the Startup tab. Look at the Location column. All of the startup
items that are started from registry entries appear first (at least on my
machine) and then come the items located in the startup folder, called
"Common Startup". You may also have entries marked simply "Startup."
Review the list to get an idea of what is where and (make a list if you
want) then click Cancel at the bottom of the System Configuration Utility
and post back. At least you will have some idea of what start up items you
can affect without editing the registry. You can find all of the Common
Startup programs in All Programs/Start Up.
The next question is, Which items in the notification area do you not need
there? That is, which programs can you just as well run from the All
Programs menu at point of need? A lot of programs simply don't need to be
run at start up.
Some services will appear in the notification area only while they are
running and then close. These do not appear in the Past Items list.
Finally, what problem is the Past Items list causing you that leads you to
want to shorten the list?
