I can't Open iTunes. HELP PLEASE?

Hi, so I click on my iTunes Icon, then it says:

'You cannot open the application "iTunes" because another user has it open.

Ask the other user to quit the application, then try again'

NO OTHER USER EXISTS ON MY LAPTOP, I have Windows 7 if that's useful.

I have read everything I could find on this problem and nothing I read solved it.

I've re-installed iTunes completely (that worked for the first time i opened it, then it came up with the error again), I've uninstalled Bonjour, closed any process /service / task / etc. that I can find to do with iTunes on my laptop, tried running as admin, logging on / off, restarting and all that.

I am on a shared internet network, but I've asked EVERY other person on the network if they have iTunes open and they all said no so...

The only thing I can think of is that I have got media sharing on, although I tried switching it off and it did nothing. The problem is, I have iTunes media sharing on, and if that is the problem (which I doubt it is), I can't even open iTunes to switch it off.

PLEASE, PLEASE, PLEASE, HELP. Anything will be appreciated, I NEED this fixed.