I am very picky with the security apps that I use on my computer. After some research and searching I have found good firewall and antispyware apps. Antivirus apps, however, proved to be more difficult to cope with. I am running vista home premium on an dell inspiron 1521 laptop. After using the free version of avira I decided to give this app a go based on the fact that avira started up a little slow and this one has been claimed to be fast at startups. I was very impressed. Tons of features and functionality were packed into this free app. Avira did not offer nearly any of the options or functionality that I received with avast. The program is very fast at startup and has no compatibility issues with any other software on my computer. It performed very well in the meager tests I through at it. I downloaded a fake virus and it stopped the download and warned of a trojan virus. It also found one or two trojans on my computer that avira did not find. Although I do not think they were trojans, they were old legacy apps I managed to install. The realtime protection offers many options from web shields to p2p shields which are all enabled when you first start the program. It also has a VRDB database that copies important system files to role them back in the event that a virus does infect a system file, similar to system restore. Overall, an excellent piece of software.