The account was created when you installed the Windows .NET Framework
1.1
update from Windows Update.
The account is used by .NET Framework enabled applications to run in a
lower
and therefore a more secure context then running under your account
(which
may be an administrator or some other highly privileged account).
Removal or modification of this account may break any .NET Framework
applications. (There are already a few out there and significanlty
more on
their way).
"Borrowed from "Mike Brannigan [Microsoft]"