Please note that this port is not supported at all by alch so don't bother him about it.
To make it work you need to download this version of the dll https://oss.netfarm.it/clamav/clamwin/ExpShell.dll https://oss.netfarm.it/clamav/clamwin/ExpShell.dll
and overwrite the one in clamwin "bin" installation directory then you must apply this registry file, but before
make sure to set the correct paths https://oss.netfarm.it/clamav/clamwin/ShellExt-64.reg https://oss.netfarm.it/clamav/clamwin/ShellExt-64.reg

Thanks! I was just thinking about making 64 bit build. Could you please add the .proj and .sln files to SVN and I will include it in the next release.

shellextimpl needs some mods, I compiled it modifing your build.bat lol so no projects
I can commit changes but I prefer you check first if it still compiles in your environment,
shlobj.h from platform sdk changes a bit the proto (I'll send you the patch, fixed also some minor warning)

we should move away form vc2003 toolkit and use vs2005 projects