Here's my thoughts on Returnil (what I'd say to friends, etc if asked, but written out in the form of a general statement.)
Returnil is an impressive new program to protect your a computer running Windows from a wide variety of viruses, spyware and malware. It does what's called "light virtualization."
That means that when it is enabled, any changes to your primary hard drive are effectively "written in pencil" and when you reboot... guess what? Yep, any changes "penciled in" are gone. Sorta like the commerical... "What happens in Returnil, stays in Returnil."
"But what about those photos I just received? I want to keep them!"
Returnil features the creation of a "virtual drive" where you can copy all those files you want to keep after a reboot. It's called a "virtual drive" because it's actually really a special big file that Windows believes is another hard drive. All version have this feature.
Also, it features Virus Guard, "Real-time Virus Protection", which you can disable it you want to use or already have a heavy-duty anti-virus or security suite installed. That that calls for a quick word on anti-virus software.
For the average user, as much as I hate to say after years of justifiably loathing this product for being such a resource hog and trouble-maker, I have to recommend Norton Internet Security Suite 2010.
It's extremely simple to install and use. Very few steps and customizations are needed and there's very, very few pop-ups to confuse the average user. It has a good firewall and an excellent parental controls that are difficult to circumvent for those who need that sort of thing.
For the technically oriented Norton is simply OK, it consistently scores well in anti-malware testing, but there are more robust products that offer much greater control and customization. At the top of the list is Kaspersky due to it consistently scoring at the head of the class in recent testing and for its built-in sandbox technology.
Of course, there really is no such thing as a clear choice for a techie. There are simply too many ways to configure a machine to suit an enthusiast's tastes and needs. Plus, there are too many possible ways to harden a machine against malware.
Other advanced options to consider, pick and choose from would include:
- Implement a Disk Imaging system: lots of choices, such as Paragon's frequent freebies, but some "bare-metal restoration" system is absolutely critical for safety and peace of mind.)
- DefenseWall HIPS
- Sandboxie
- Implement a Software Restriction Policy (info here); also check out SuRun here and here.
- FirstResponse-ISR (possibily revitalized and updated for Windows 7; announcement coming 1st quarter of 2010)
- Peruse the wealth of knowledge and information provided on Raymond.cc's Spyware/Viruses forum
- {Your options here.}

Returnil is definitely worth seriosuly considering. There have been several opportunities to get a one year subscription for the paid version for free. And there is a free version as well.
Make some malware very unhappy,
install Returnil today.