how to Completely remove Oracle 11g from my computer?

From Manual and Clean Uninstall Oracle for Windows :

1. Uninstall all Oracle components using the Oracle Universal Installer (OUI).
2. Delete the HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE key which contains registry entries for all Oracle products by using regedit.
3. Delete any references to Oracle services/components in the following registry location:HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/. Looks for key entries that starts with “Ora” which are obviously related to Oracle.
4. Reboot the workstation.
5. Delete the ORACLE_BASE directory. (i.e C:\Oracle)
6. Delete the C:\Program Files\Oracle directory.
7. Empty the temp directory.
8. Empty the recycle bin.

http://superuser.com/questions/256762/how-to-completely-remove-oracle-11g-from-my-computer

How to login to the scot account after installing Oracle 11g [closed]

I think you have not unlocked your scott user account while installation,please follow the steps below to unlock you scott account .

When you started installing oracle ,it asked for global database name and database password that password is used for the sys system sysman dbsnmp account.

1. SQL> conn user/password;
   SQL> conn scott/tiger;

Error message is displayed: the account is locked.

1. Try to login as "system" - pass
   SQL> conn system/password;
2. Unlock "scott"
   SQL> alter user scott account unlock;
3. Can change "tiger":
   SQL> alter user scott identified by tiger;
4. SQL> conn scott/tiger; -Success

scott account is locked in 11g due to security thinking,

Now you can type Connection Name :ORCL ,username:Scott,password:tiger to login

http://stackoverflow.com/questions/9862364/how-to-login-to-the-scot-account-after-installing-oracle-11g