Well, Microsoft is playing it safe in respect to the installation of Internet Explorer 7. And although Microsoft has failed to confirm IE7 installation problems related to anti-malware applications. It has argued that it is better to prevent implementation issues by temporarily disabling anti-virus or anti-spyware applications.
“Along with copying IE7 files to your system, IE7’s setup writes a large number of registry keys. A common way anti-malware applications protect your computer is by preventing writes to certain registry keys used by IE. Any registry key write that fails during setup will cause setup to fail and rollback changes. We work around the problem in most instances by checking permissions at the beginning of setup, but many anti-malware programs monitor the key rather than change permissions. Therefore, setup thinks it has access when it starts, but then fails when it later attempts to write the key,” explained Hrvatin.
Microsoft could lose the disabling anti-malware recommendation as the browser's setup will present digital signatures or file hashes to third party security software. But not until Microsoft can ensure a minimal risk of failed installation.