There are two VSE components that can help here, depending on how agressive you want to be on Y!M and Live Messenger (as it's called these days):
- Access Protection: Create a File/Folder protection rule to prevent creation and execution of Y!M and Live Messenger EXE (names not on top of my head).
- Access Protection: Create a Port blocking rule to block ports use by the two IMs (make sure you are not blocking a port you use for other apps).
- Unwanted Program Policy: Add the EXE's of the 2 IMs to PUP policy. PUP only take action if exact match of file name is found, so only effective with non-tech savvy users.
Thank you ! I will try it !