LANDESK does install a few things to the C: drive on a Core Server. They are basic agent type things, but not the full agent. Unless "YOU" actually deployed the agent to the Core Server. In that case, you are going to have a lot more space used. The Core will then be an agent. You may be deploying software or patches to the Core Server and those will go into the sdmcache folder.
Did you deploy the agent? If so, you may get your space back by emptying the sdmcache directory.
Otherwise, You can follow v.taillet's idea of using a symbolic link. Just xcopy the C:\Program Files (x86)\LANDesk directory to another drive and then delete the C:\Program Files (x86)\LANDesk directory (you may have to stop a lot of LANDESK services to do this) and re-add it using a symbolic link.
Another option is to actually mount a drive as that directory.
EIther solution is basically the same.