Forget downloading all the spyware programs, I have a very simple and 100 % effective way to stop Limewire. I have been having the same problem with Limewire starting on its own and not being able to shut it down. And everytime I would uninstall and reinstall it. This would help, but only for a little while, then it would do it all over agian.
Now, Start your computer in safe mode (while computer is booting up, hit F8 repeatedly to get it to enter safe mode) Now mind you this is XP I'm working with, so if you have another operating system, I hope this still applies. When in safe mode, go into My Computer- C drive- documents and settings- all users- start menu- programs- startup.... then in there if there is a file called svchost (it will be an .exe file) delete it. This is what starts Limewire and it gets downloaded to yur computer everytime windows does and automatic update. It is a windows file, but is unnessesary and only causes problems. At least it does for me, and this is the only way I've ever been able to get limewire to back off. Deleting it has never causes my computer any problems, I hope this helps someone out there