NetBEUI was a protocol that 3com & Microsoft had developed for use in networked products such as Lan Manager. One of the biggest shortcomings in the NetBEUI protocol is that it can not be routed, as it has no concept of networks. Thus any large networks will have to be bridged and end up being too 'talky' and are unreasonable.
NetBEUI shouldn't be in any serious use anymore.
You can find some great information on clients for MS-DOS here.