SLK is full of limitations and is not really a good choice as a substitute for an full LMS. But I imagine ou are inside a corporate structure and haven't really been given a choice in this?
I'd really advise dropping it and putting the effort into something like Moodle, Claroline or similar using a log in likned to the networks usual user details. Using LDAP on the client side is quite well documented.
I work in a big health group with 2 major hospital sites, 6 minor ones and numerous other sites, there are over 10K employees of various types. We have a common network and COIN spanning all the sites and the intranet structure is all built on MS products. A pretty standard UK NHS set up.
Did we deploy SLK?? No we have a dedicated LMS as it works far better than SLK.