Startup rootkit scan

Why in the 64 bit version is the setting “Enable Rootkit scan on system startup” enabled?

http://img195.imageshack.us/img195/6373/semttuloayf.png

It is a default setting on 32bit OSes also.
It doesn’t actually happen during the system startup but 8 minutes after startup.

Or are you saying that 64bit OSes can’t get rootkits and as such don’t need this ?

The second option if a 64 bit OS can’t get rootkits why is this option enabled ?

I don’t know for certain if they can or can’t, but a google search seems to confirm that they can get rootkits, http://www.wilderssecurity.com/showthread.php?t=254084, there are other references. There are now some anti-rootkit tools that support 64bit OSes, so I wouldn’t have though it worth their while to do that if it wasn’t possible.

That is why I asked you “are you saying” 64bit OSes can’t get rootkits.