Do you have a SIM card inserted in your device? Can you confirm that the OS is specifically for your model. Your profile shows 9780 and there is no OS 7 for that model, although your post does say 9900. Please update your profile.
There have been several problems updating to the latest release. Are you following the instructions for OS7 updates? I recall there are a couple other places to delete the files. Maybe try a search and see if you can find it?
This also might help: Leaked OS 184.108.40.206 for the 9900