I've run into a problem when upgrading from ZFD 4.01 to ZDM 6.5SP1b, and
need to mass modify the availability/system requirements options for
over 1000 app objects.

ZFD 4.01 app objects have availability/ system requirments set as below
to ensure they only deploy to XP workstations and not legacy 2000/NT

-OS Version, Windows NT/2000/XP, equal to, 5.1.x-

For some reason the ZDM 6.5 SP1b agent does not display these apps on
any XP workstation.

I think this is similar scenario to the XP SP1/SP2 version thing, for
which there is a well documented TID.

Change the availability requirement to OS equal to or greater than NT
version 5.1.x. The 6.5 SP1b agent will then display the app fine.

I've read this tread re the same issue
and am in the same scenario, how do I mass modify this on all my app
objects, without doing 10,000 mouse clicks in C1?

many thanks,