I have exactly the same problem, except my OS is windows 2000 professional. I think it may be because some viruses/spyware are stopping it from opening. I know how to solve your problem, but not mine!
Go to this page, read what it says, and voila! you have no more problems.
You are about to answer a thread that has been inactive for more than 6 months. If you still wish to proceed, please ensure that your posting is original and does not duplicate or overlap any prior responses to this thread.