Windows 7 - Run As

For some reason I started getting a pop up window when Windows XP Pro
starts up. I have never seen this before and have no idea how it came
to be.
It says.
Run As:
Which user account do you want to run this program? and my choices are
Protect my computer and data from unauthorized program activity.
A sub-note says this option may cause some programs to not operate
correctly.
The second option is:

Any help greatly appreciated...

First things first. Do a full virus scan on your system. If you
found any, quarantine it. Reboot when the scannning is finished.
The popup may be caused by a virus/malware.

Try isolating the problem by temporarily disabling third party
programs that are run at startup using AutoRuns.

http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx

In AutoRuns, go to the "Logon" tab and disable all entries whose
programs) except those that are anti-viruses. Then reboot the
system.

If the problem disappears, then it must be caused by one of the
disabled programs. Refine the isolation by enabling the first half
of the previously disabled programs. e.g.: If there were 10
disabled programs, enable the first five. Then reboot. You'll have
to use this method until you find the exact culprit.