Hi Greg
i tested what you said previously.
i copy the vfp registry.prg in a new file registry1.prg and made changes in this last replacing the value spac(256) by spac(4096).
i run as administrator regedit.exe, made a fake new string in HKEY_CURRENT_USER\Software\Microsoft\VisualFoxPro\9.0\Options (see photo above) :_ayb (rightclick on pan and new value ("Chaîne" )
in vfp command command _cliptext=repl("A",4000)
,go to the key above (options) ,right click on _ayb and paste clipboard.it have a length of 4000 chars.
using the old registry.prg, this key is not retrieved at all but the code works (the cursor browsed)
using the new registry1.prg (with changes) the key is shown at browse (troncated to fit the field legth).

for 256 value the codes works in registry.prg until 253 chars value.
for 4096 the code in regsitry1 works until 4093 chars only (maybe terminating unicode chars)

conclusion : for long paths>253 length must make changes in the registry.prg to make it working. otherwise the long keys (paths for ex) are not shown.

note : can do this operation from vfp/menu/tools/options and choose a long path in 'files'
press ( values by default"+OK to save in registry