I finally resolved this issue using different steps from different people.
To summarize:
1.uninstall itunes and other apple related products.
2. look for folders related to apple and delete it. (C:\Program Files\Common Files\Apple or C:\Program Files(x86)\Common Files\Apple etc.)
3. click start, search for services.msc. Then look for an item Apple Mobile Support. (If its not listed skip step 4)
4. you need to unregister the key. here are the steps: (credits to http://stackoverflow.com/questions/197876/how-do-i-uninstall-a-windows-service-i f-the-files-does-not-exist-anymore)
1. click start, search Regedit or Regedt32
2. Go to the registry entry "HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services"
3. Look for the service that you want delete (apple mobile device) and delete it. You can look at the keys to know what files the service was using and delete them as well (if necessary)
4. Restart your computer
5. Check if its still listed in services. (click start, search for services.msc. Then look for an item Apple Mobile Support.) It shouldnt be there. If its still there, then its another problem.
5. Install the latest version of iTunes. Yes you would still get errors, rolling back action and the likes.. RELAX! the following solutions are on the following steps. Let the download finish.
a. If itunes was successfully installed but apple mobile Device is not installed. click on the following link (ITS MY HERO): http://randomwindowstips.wordpress.com/2009/12/08/windows-7-itunes-9-software-is -not-installed/#comment-2761
b. If itunes was not installed having "cant access key: error, follow the steps on this link: https://discussions.apple.com/docs/DOC-3581. Then go follow item A.
Hope these things could help you as it did to mine.