One of the big issues with Windows Vista was that the system was too strict on security, and always popped up with notifications regarding security issues. This became a big problem, because a big part of the Windows Vista users chose to completely turn off the notification feature, leaving the system vulnerable. To address this problem, Windows 7 introduces 2 new security levels (see figure bellow) in the User Account Control Settings (UACS). The first - which is default in Windows 7 - is called: Notify me only when programs try to make changes to my computer, which is a level where you no longer see notifications regarding you messing with the settings in the Control panel, but only if a third-party program tries to. The second is called: Notify me only when programs try to make changes to my computer (do not dim desktop). This level will further stop the UACS from utilizing the "safe desktop" and the desktop light will not dim, and you will be able to run other programs while UACS messages pop up. It is no longer possible to turn off the UACS completely, but you can tell the UACS to never ever inform you of anything.
In Windows 7, the Security center has been replaced with the Action Center, which now contains the functionality of Computer Maintenance and Security. Here you are now able to adjust the notifications according to a given subject, e.g. if you no longer wish to see information regarding virus protection or network firewall, you just uncheck the subject from the list. Off course this doesn't improve security, but it removes the hassle of administrating the system. In fact, Windows 7 has pushed even more security settings in, when compared to Windows Vista, but it also introduces problem solving tools, which is problem solving wizards which check your program and security settings for problems, and tell you what they find.
AppLocker is a new feature to Windows 7, which easily lets you which programs different users are allowed to run. E.g. You can tell AppLocker to trust all software coming from Microsoft (or others) and AppLocker will run all software signed by Microsoft, and you can stretch this into also telling AppLocker that newer version of a give piece of software is trusted, and these will also run without problems. This feature though is only provided with the Windows 7 Ultimate edition.
PC Safe Guard - or as I like to call it; Annoy-Your-Teen - is essentially a kind of sandbox account. It lets you create a user account and set it up with the software you want, and then activate PC Safe Guard. PC Safe Guard then makes sure that all software (and spyware or viruses) installed after activations is deleted when the user logs out, and this way the user account returns to the state of first-install. Files created in an PC Safe Guard activated User Account, must be saved on another partition of the hard drive, where PC Safe Guard will not touch them.
BitLocker is a feature that was also present in Windows XP and Windows Vista. In these versions though it was not always easy to find, but all this has changed in Windows 7. Now all you have to do, is right-click the hard drive and select "turn on BitLocker", and an easy guide will follow you through the process. This feature is only available in Windows 7 Ultimate, which I find rather disturbing. Microsoft has a portal called MSDNAA where students from around the world (if the university they attend to has signed up for MSDNAA) can download Microsoft products for free (while being students). This portal gives the Windows 7 pro. Version to students and faculty teachers. With this in mind, there is lots of research going on at these universities, where encrypting of hard drives could be a nice feature. So why not make BitLocker available to lower versions of Windows 7?