I found this:
Some computer security software, such as
McAfee's
McAfee VirusScan and
Symantec's
Norton AntiVirus, works by patching the kernel.[
citation needed] Additionally, anti-virus software authored by
Kaspersky Lab has been known to make extensive use of kernel code patching on
x86 editions of Windows.
[15] This kind of antivirus software will not work on computers running x64 editions of Windows because of Kernel Patch Protection.
[16] Because of this, McAfee called for Microsoft to either remove KPP from Windows entirely or make exceptions for software made by trusted companies such as themselves.
[3]
Interestingly, Symantec's
corporate antivirus software
[17] and Norton 2010 range and beyond
[18] does work on x64 editions of Windows despite KPP's restrictions, although with less ability to provide protection against zero-day malware. Antivirus software made by competitors ESET,
[19] Trend Micro,
[20] Grisoft AVG,
[21] avast!,
Avira Anti-Vir and
Sophos do not patch the kernel in default configurations, but may patch the kernel when features such as "advanced process protection" or "prevent unauthorized termination of processes" are enabled.
I wonder how Sandboxie was able to deal with this problem?