The “avast! antivirus” has many different versions with support for many computers and operating systems. Some “Home” versions are released with annual registration (and re-registration) that is free of charge for non-commercial home use. It is recommended to check the avast! Latest Program Version Matrix before downloading any of the hyperlinked versions. This is because several products have home pages with major version numbers in their URL, and so it wouldn't be surprising if newer software versions may have newer home pages.
According to the product's home page, “avast! 4 Home Edition is free of charge for non-commercial home use“. It appears that free annual registration is required (as noted in more detail in the section of the “avast! Linux Home Edition”).
Although the home version download may identify itself as the “Home/Professional Edition”, the download links for the home version and the professional shareware version are in fact different (and point to files with different file sizes).
When the system requirements for avast! were checked online with version 4.8, they were found to match this lenient description that was found in the installation program's output: “avast! 4.8 antivirus protection” “Home/Professional Edition” “for 32-bit Windows operating systems: Windows 95/98/Me/NT4/2000/XP/Vista and 64-bit version of Windows XP/Vista.” The avast! Antivirus and Windows x64 Edition page says “that all avast! antivirus editions, including the free Home Edition, now fully support the new Windows x64 platform (avast! Server Edition supports both x64 and IA64 (Intel Itanium) platforms).” That parenthesied note sounds important for IA64 users if a separate “Server Edition” is needed.
Version 4.8 added support for anti-spyware protection and, for Windows 2000/XP/2003/Vista/2008, anti-rootkit protection. (The other features of the avira! antivirus “Version comparison” page that was noted as being limited to operating systems were “Self-defense (protection of antivirus processes, files and registry keys)”, which had the same operating system requirements as anti-rootkit and was listed on the “What's new in avast! 4.8” page along with anti-spyare and anti-rootkit, and boot-time scanning in 32-bit versions of WIndows NT/2000/XP/2003/Vista/2008.
To keep this section brief, this paragraph discusses differences from the “avast! 4 Home Edition” product. The description of that product contains details, such as system requirements, which are likely to apply to this version as well. avast! 4 Professional is shareware, according to avast! antivirus - Versions comparison. It also supports additional features, such as a command line scanner and storing scan results in a history. avast! 4 Professional Pricelist
avast! 4.x VPS page says “Updates are released at least twice a week.” avast! antivirus - Versions comparisons refers to “Incremental updates of virus database (VPS)”. (There is a page with VPS history.) The dates reported on the avast! Latest Program Version Matrix do appear to be in European notation, so 29.10.2007 refers to the 29th of October, and obviously not using the American style notation where such a date entry would look non-sensical, referring to the 10th day of the 29th month. The date on the VPS page matched the one on the “Latest Program Version Matrix” when checked.
The web site largely refers just to the major version number (such as “avast! 4”, including the hyperlinks for the individual downloads (for the home version and the professional version in multiple languages). The best way to ensure the latest version is being obtained may be to check the avast! Latest Program Version Matrix, which has a URL that appears to be independent of any version number, unlike the web pages for some of the individual products (including the freeware and shareware releases for the most mainstream versions of Windows). The latest version number showed up on the left frame. For example, a hyperlink with the quoted description: “What's new in v4.8&dquo; of avast! showed up when version 4.8 was the latest. There was also a hyperlink called Revision History with a URL that seemed specific to the latest major version number. Revision History of avast! 4 gave specific details, including the build number (4.8.1169) and a list of new features. That page could likely be used to effectively check versions as long as the major version number (meaning the part before the first decimal point) hasn't yet changed.
There are numerous languages, including avast! 4 Home Edition: English release.