It's a library for a piece of spyware called CyDoor. It is bundled along with Kazaa amongst others and chucks up adverts that never offer anything of any use. It can be removed with Lavasoft's AdAware, as can most other pieces od ad-ware, spy-ware and general rubbish. One day, the internet community will unite and not buy a single thing advertised using these methods: then the companies involved will go bust and never again bother us in such invasive ways...
Thank you for the response, I've been using Lavasoft Ad-ware, but unfortuneately it didn't remove the clint.dll. I've found it in my Windows System file and it won't delete.