updaterui.exe usually belongs to the McAfee Enterprise application and should reside somewhere in the McAfee installation directory, normally in a subfolder of "C:\Program Files". In this case, it's a required component for your security.
If it resides anywhere else, then it's possibly a virus.
As companies such as McAfee are adding tens of thousands of virus descriptions daily to their virus database, then naturally lots of I/O is required to update the database. It's then quiet normal for this process to heavily use I/O.
If you think McAfee is slowing down your computer (and you won't be the first), uninstall it and find a better and more efficient antivirus. There are currently several excellent ones that are free for personal use, such as Avast, Avg, Avira AntiVir, Microsoft Security Essentials.
What program/application does UpdaterUI.exe comes from? Can you link us to its homepage? – badp – 2010-09-03T10:52:53.453