Yes. it's called UAC.
However, as you described, I don't think that's the case.
for a Limited User Account, the UAC dialog allows them to enter/get somebody to enter the administrator password- then the process will be run as administrator.
For many people (my case, for example) their own accounts are set up as the administrator, but due to new security settings the "administrator" roles are stripped out of their access tokens- so they no longer really have administrator access. In this case the UAC dialog still appears (if UAC is disabled, then there is no additional security, since this part is skipped) but is asking the user (who is an administrator) to continue. the idea here is to prevent programs from performing tasks at the administrator level without the user knowing- this was a common tactic of malware (they didn't have to ask for administrator access, since they were already running as the administrator).
I've never seen the OK button disabled before though.
