Microsoft blocks Atsiv Vista utility to prevent unsigned driver loading
 

Microsoft has acted to prevent the continued function of a free utility designed by LinchpinLabs. Up until now, Linchpin's Atsiv utility could be used to load unsigned drivers into the operating system's kernel. Atsiv itself used a signed driver, but once installed, was capable of loading other, unsigned software. Microsoft referred to the program's functionality as ''rootkit behavior,'' but LinchpinLabs defended the program as a means for users to load legitimate unsigned drivers they might require.

http://arstechnica.com/journals/micr...driver-loading