Vista - Spybot-S&D - Alter Ego - making your online activity more secure

Modern Windows versions allow you to set up multiple users with differentiated rights, ranging from administrators to regular users. For various reasons, ranging from default installation settings over the requirements of carelessly written software to laziness, most Windows users are using an user account with administrator privileges in their daily work.
Windows also allows you to run each application with the privileges of a chosen user account. So, while we grudgingly accepted that we won't change people to use restricted user accounts in their daily work, we've decided to pursue a compromise: determine which applications are endangered the most, and allow the user to run those with restricted rights only.
Now, since comfort is the issue that's restricting most users, either directly or through people having set up their system, from using restricted user accounts, we tried to make this process to be as easy as possible, which resulted in Alter Ego. Alter Ego is an application that makes your browser, email application, instant messenger and multimedia player run safer with just three clicks: click here for an animated demonstration.
Visit this forum thread for more information and discussion.

The Problem: software run by an admin account can do anything to the system (Vista at least has UAC there).

The Solution: use a standard user account for daily work, and reserve the admin account for your rare administrative tasks.

The Alternate Solution: knowing that you would just nod your head and yet ignore it if we recommend that non-admin account, we turned a hidden feature of Windows around. Windows allows you to run single applications under a different user account. Usually, we would recommend to use that to run admin applications from a restricted user account, but since we mentioned we've 'given up' asking you to change to that, we've decided to help you using the most endangered types of applications (browsers, email apps, IM apps, multimedia apps) through a restricted user accout instead.

The Implementation: close your applications, run the Alter Ego wizard, click Next three times, click Exit. That's it, unless you want to fine-tune things. Run your applications as usual (shortcuts will have been replaced), your settings have been taken over to the alternate account, you won't notice a difference. Well, except that you won't be able to save your downloads in C:\Windows\, because your Alter Ego is not allowed to do so. But neither could malware install there.

Just a copy/paste from the topic on the forums about Alter Ego