My advice would be don't use them but that's a different and longer story. 

Could it be capitalisation that's the problem? You can tell by inspecting the object with the Agent Explorer to see how it's expressed.

You could try: WORDPOS(UPPER(EDMGETV(SMINFO,SYSPROD),'VMWARE 8650W 9470M'))=0

WORDPOS uses the entire value of the first parameter when searching the second. For instance, my SMINFO.SYSPROD reads HP Compaq 6000 Pro MT PC so it would search for that complete string inside the second parameter which you specified 'VMware' and there would be no match. You could reverse the strings and user WORDPOS('VMWARE', UPPER(EDMGETV(SMINFO,SYSPROD)))=0 which would then allow installation on all machines where SMINFO.SYSPROD contains the word VMware. You can also use ZCONFIG.HWMODEL in place of SMINFO.SYSPROD.

If there are multiple versions of VMware and you want to limit it to one you would have to expand your search string. Say I wanted to limit mine to 6000 Pro versus any other 6000 model I would use WORDPOS('6000 PRO',UPPER(EDMGETV(SMINFO,SYSPROD)))=0.

Thats also not help :(

Please copy and paste your zstop and sysprod values.

Use the Agent Explorer to open the SMINFO.EDM object on the client (in <ClientInstallDirectory>\Lib\RADSETUP on my machine) to check what the actual value being sent during resolution, then make sure that value in in the second parameter.

e.g. if the SYSPROD value is 'HP Compaq Elite 8300 SFF" then you would need to have that in the second parameter - i.e. WORDPOS(EDMGETV(SMINFO,SYSPROD),'HP Compaq Elite 8300 SFF')=0

Having multiple model types means having each of the entries concatenated EXACTLY as they appear in SMINFO...

e.g. WORDPOS(EDMGETV(SMINFO,SYSPROD),'HP Compaq Elite 8300 SFF Dell Optiplex 760')=0

Be mindful of the length of the ZSTOP attribute though...

All is clear now. Thanks all for your help.