Thank you for your quick reply. I investigated a little bite on my site and went to another Forum http://www.planetamd64.com.
And found following information.

Things to read about 64 bit windows before posting.

  1. There are currently NO updates for windows 64 except for RC1 and later versions…
  2. There is NO flash support for windows.
  3. You should NOT use 32 bit firewalls and Antivirus software on 64 bit windows. Avast Antivirus 4.5 is recommended…
  4. No 64 bit windows for AMD is not released yet. (Just the CPP beta versions, RTM will be in late March 2005)
    Last updated on Jan, 11th 2005 by }SkOrPn–'<

OK, I am using avast Server Edition - this is not necessary for XP 64-bit (but is necessary for Windows 2003 Server 64-bit). Could you please let me know what would be the right Avast Antivirus 4.5 for me?