Microsoft Security Essentials 2.0 - Mediafire
Microsoft Security Essentials 2.0 - Datafilehost
Microsoft's free anti-malware for Windows
While much of that may be down to the cost, compared with much of its competition, it's also a well-designed anti-malware tool with both anti-virus and anti-malware capabilities.
Available for Windows XP (Service Pack 2 and higher), Windows Vista and Windows 7, and in both 32- and 64-bit form, Microsoft Security Essentials is part of the Genuine Windows programme, and can only be used on consumer PCs.
Small businesses do have an exemption, and can run it on up to 10 machines; any more than that and you need to use Microsoft's Forefront Endpoint Protection tools. It's a small download, the latest beta version is 9MB for 32-bit machines, and 11MB for 64-bit. [techradar]