Most probably reason would be in your machine performances. Because, “Oracle 11g” used more CPU processing power and also used bigger hard disk space. So I suggest you to turn off start up process related to Oracle 11g process, in System Configuration menu (Go to run-> msconfig).
Not only that, Change the startup type setting into manual for all Oracles processors in services panel.
(Go to run-> services.msc)
Then reboot machine and check your pc performances.