I'm quite happy with my current security settings and I don't need a little info bar taking up precious real estate in my Internet Explorer 7 browser to tell me:
"Your current security settings put your computer at risk. Click here to change your security settings."
Sometimes you need lower security in Internet Explorer 7 for testing, development and demo's. Anyway, once you accept that you are a horrible person with less than adequate security, the only way to disable this infobar is in the registry.
Go to:
HKCU\Software\Microsoft\Internet Explorer\Security\
and add the following key: DisableSecuritySettingsCheck as DWORD and Value of 1