Q: iTunes problems

Hey!

I have some problems with iTunes. Yesterday iTunes started an update but it didn't worked and I had to remove and reinstall iTunes. But now, the installation does not work too and I always get the message: "Service 'Apple Mobile Device Service' failed to start. Verify you have sufficient privileges to start system services"...
I tried it many times and I also checked if all components were completely removed (previous to installation). I also ran the installaion as administrator but nothing worked.... I have absolutely no idea what I should do now. (My operating system isWindows 7)

So please help me!!!!

Thanks a lot!