Reboot the PC into Safe mode by tapping f8 repeatedly when the system is starting up. In the selective startup select safe mode. When it loads you will see the administrator account - use it. In the administrator account go to start > control panel > user accounts > user accounts > click create a new account > give it a name that you'll remember > set it to computer administrator > then you'll need to restart and hide your account. Once restarted log in with your username and follow these steps to hide your username from the welcome screen:
1. You begin by opening the Registry Editor. Do that by clicking Start -> Run..., type regedit and hit Enter.
2. With the Registry Editor opened, you want to expand the following keys: HKEY_LOCAL_MACHINE -> SOFTWARE -> Microsoft -> Windows NT -> CurrentVersion -> Winlogon -> SpecialAccounts -> UserList.
3. On the right is the list of accounts hidden by the system. To enter a new one right click and select New -> DWORD Value. This value should be named the same as the account you want to hide.
4. Reboot the system, and you will notice the account will disappear from the Welcome Screen. Still if you want to log on into the account, hit CTRL ALT DELETE twice, type the name of the account and password if necessary and log into Windows.
5. To get everything the way it was delete the key you created in the Registry Editor.
You may also need to reinstall the game onto your profile but it should still work without reinstall. Good Luck HTH.