What to do when my computer freeze?

What to do when my computer freeze?
My computer likes to freeze, but I can still move my mouse. I think this all started when I first got an error message. It only shows up when I start the computer. The name is RUNDLL and it says "error loading C:Windowssystem32bmwduwvu.dll.
The specified module could not be found." My computer is also very slow too. I'm freaked out when my computer was like this. I really don't know what to do.
Anybody knows this kind of problem?
What happen to my computer?
What should I do to solve this problem?
How can fix it?
