Ah, sorry...my programmer life is interfering with my Windows life. UAC...User Account Control. This should NEVER be at the lowest level. Ideally, for people who have a real problem with malware...it should actually be jacked up, so that such users are warned MORE often when they may be installing something malicious.
Most users turn it off completely, which is terrible, and is largely what leads to the terrible experiences they end up with because of the kind of junk they install. Malicious actors take total advantage of the naiveté of most windows users with regards to this feature, which is why there is so much malicious third party content out there for windows.
It is actually possible to enable it, and also deny the ability of normal users to change it. If I know someone who is particularly bad at downloading crap programs that are the root cause of their problems, I will usually try to get them off of an admin account, if they are on one, create my own admin account, and use windows security group policies to disable their ability to change the setting themselves. Now, it won't necessarily prevent installation of malicious content, but it can definitely warn the user more frequently when they are installing something, and will make them think a bit more about installing stuff. You can also just disable the person's ability to install entirely, if they are a particularly...erm, troublesome user.
Microsoft really needs to do a better job educating users to these features, maybe as part of new computer setup and new account creation, or something, so that people fully understand the risks they are taking if they disable security features built into windows that are intended to save them from WinHell.