I need to know which client versions of Oracle different people have installed on their PC. Anyone have an idea how I could find that out, if possible remotely? Or if nescessary, I can give the people an instruction to view their installed versions... but I don't know which. I don't want to have them find every version of SQL*Plus on their system and start it to see what version it is ....

Any suggestions??

OK, I figured something out myself :-)

I guessed every Oracle Client installation has a TNSPING.EXE or TNSPING80.EXE. For every version, this file has a different size.
So I just scan for these files, and check the size. Then I know which client versions are installed.

Works for me!