3.51 (and some digits beyond that).
Here is how to find out what version you are running even if you have done a system upgrade or applied a Windows Service Pack.
Do a Find Files or Folders on file MSJET*.DLL
Select (single left click) the .DLL file that pops up when you do that. Should be only one MSJETnnn.DLL file, but the number 'nnn' is not the full version number of the Jet engine.
Right click on that file in the Find window.
In the pop-up menu, click to bring up Properties.
One of the property tabs is "Version." Select that. You will see the detailed version string as it currently exists, including any patches or updates made to it as a result of system updates.
I think this will work for ANY Microsoft .DLL or .EXE file, but I'm not going to swear to it for other files from non-MS vendors.