I have searched and I don't find a definitive answer... I upgraded from LE to X3... do I need to keep LE for any reason, or are they totally separate entities?

The most recent version of LE is a very small subset of SONAR X1. With the exception of your post http://forum.cakewalk.com/FindPost/3005237 there is no reason to have LE installed. However there is little to be gained by removing it.

i would uninstall LE but never get rid of the disc

Yeah, it's a hard drive space issue, so I was just trying to find out if there were any shared functions between the two that would give me issues, so thanks, good to know.

I am not sure how must space an LE instance consumes but removal SONAR Producer frees up about 200MB. An instance of LE would be less than that.

If HD space is a concern, maybe it's time to invest in more capacity.
 
Removing things like Sonar LE won't do much at all to free up space.

I am not sure which OS the OP is running, but in Windows Explorer you can search a hard drive quickly by size. In Win7 searching by "gigantic (>128MB)" or even "huge (16MB-128MB)" can be a big eye opener. Some programs leave nasty caches behind which are not required, and you do not even realize they are there until you see this search performed. Many of these programs can have there caches set to someplace more obvious (by you) so that you can purge them more regularly. Another "junk directory" that can accumulate fast is "C:\Users\[username]\AppData\Local\Temp"