1. Open Device Manager (Right click on start button) and uninstall AMD and Intel drivers under Display Adapters. While uninstalling, select "Delete the driver software for this device".

2. Now from hereon , there are three options, try whichever works for you.

A.1  First, install the latest Intel HD 4000 drivers from Intel website. Intel also has a tool that will auto detect the relevant drivers and softwares for your system. http://www.intel.com/p/en_US/support/detect or this is the link for the latest Intel drivers -https:/downloadcenter.intel.com/download/24973/Intel-HD-Graphics-Driver-for-Windows-7-8-8-1-64-bit" title="Intel HD 4000" target="_blank" rel="nofollow noopener noreferrer"> https://downloadcenter.intel.com/download/24973/Intel-HD-Graphics-Driver-for-Windows-7-8-8-1-64-bit

A.2 Restart your system

A.3 Now install the latest beta drivers for AMD Radeon HD 7700M. Either use the auto detection software or download from here - http://support.amd.com/en-us/download/desktop?os=Windows+8.1+-+64.

A.4 After installation, restart the system. Now go to control panel and check for updates. If there is any optional update for Advanced Micro Devices, Inc. - Graphics Adapter WDDM1.3 - AMD Radeon HD 7730M, size: 63.5 MB, then don't update it and hide this update. Now the switchable graphics should work fine.

OR

B.1 Go to dell support centre - http://www.dell.com/support/home/us/en/19/product-support/product/inspiron-15r-se-7520/drivers.

B.2 Put in your service tag and let it analyse your system and download the intel and amd drivers.

B.3 Restart your system and again, don't install the above mentioned optional update if there is one.

OR

C.1 Install intel and amd drivers package from leshcatlabs.net. Here is the link -  http://leshcatlabs.net/downloads_unfil/ (Catalyst 15.4 Beta 1 UnifL v2.0).  Run the installer and it will auto detect the required intel and amd drivers for your system.

C.2 Restart the system and again, don't install the above mentioned optional update.

Now for gamers, after doing above, to run any game smoothly, change your power plan (Battery Plan) to "High Performance". Open Intel HD Graphics Control Panel, navigate to "Power" tab and change the power plan to "Maximum Performance" under both the tabs of "Plugged In" and "On battery" as per your requirements. Configure switchable Graphics in the AMD Catalyst Control Center and add your games there and change the "Graphics Setting" to High Performance.

Hope this helps.