Boot time scan for x64 Avast! Home

Hi, I’m wondering whether I can or why I can’t run a boot time scan on my Windows XP Pro x64 system. The FAQ says only NT operating systems can run the boot time scan. WinXP x64 is technically an NT operating system, so it should be able to schedule a boot time scan, right? But it’s “greyed out”!

I appreciate any advice!

As far I know, the x64 systems have a different boot scheme and, yet, avast! does not cover it at boot time. In fact, a lot of boot time programs aren’t working on x64 systems… Maybe I’m wrong. Just think I’ve read this on the net some time ago.