you have to be very careful deleting .dll's Some are required for your pc to run. That said... you can try deleting it in safe mode. Have you tried a system restore? You might be best off running the "hijack this" and posting your results in their forum for the experts to guide you. I don't have the URL handy... do a search for hijack this or get it from one of the previous links.
there may be a task running that using it. if you kill the task, then you can delete it. But as someone else said, you have to be careful deleting dll, many are shared and some needed by the system. best to research the name of it to make sure it's a bad one first. then use task manager to kill the task associated with it. then you should be able to delete it. tricky stuff... be careful.
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