Schedule Boot-time Scan -- greyed out

I am trying to get rid of a virus. Every time I run a scan, it shows the same or similar virus which it gleefully “moves to chest” only to reappear later. (“deleting” virus works no better)
So now I want to schedule a Boot-time scan – something I have done before, only now that option is greyed out! Is that caused by the virus trying to protect itself from deletion, or what? There must be a way I get a boot-time scan going on.

If you have Win XP/vista 64bit then there is no bootscan, try safe mode

But you say you have done it before? on this computer?

Have you tried MBAM http://filehippo.com/download_malwarebytes_anti_malware/
Or SAS http://filehippo.com/download_superantispyware/

No, actually – not on this computer. I used avast for years, and now have a new computer running Windows 7, 64 bit. Just got the latest version of Avast (4.8 - waiting for version 5), so I didn’t expect it to have reduced functionality on this platform.
I read somewhere about being good on Win 7, but they also mentioned version 5. So: is there a beta, or what (or when)?

Sorry, the boot-time scan is currently not available on 64bit OSes - neither in avast! 4.8, nor in 5.0.

avast! 5 is coming… soon! http://blog.avast.com/2009/07/20/avast-5-is-coming-soon/#more-354

@tree

I am using Windows 7 64-bit and I use Malwarebytes’ Anti-Malware and they work great together.

The free version requires manuall update then run a Quick scan and let it remove what it finds.

You can include its log file here if you like.

V5 avast! will be available by the end of this month I believe.

A Quick scan or a Full scan can be run from the avast! V5 Graphic User Interface.