As a great necromancer, I shall resurrect this thread, because it has not been fully answered.
I was searching for a solution to this problem. There was no convenient solution around, so I decided to fix it myself and share the knowledge as a good person. 🙂
My laptop is ASUS K56 and it has an Ivy Bridge i7 CPU, 8 GB RAM and NVIDIA GT740M GPU, so it should be more than sufficient to display the 3D OSD. But it isn't. This implies bad coding from ASUS.
The problem is that the 3D On-screen display (OSD) is a resource hog. Note that the 3D gives a big resource hit when your laptop is using a 5400RPM 2.5" mechanical HDD. The performance hit is negligible with SSD.
Following my guide, You will replace the 3D OSD with 2D OSD, which will solve things the easy way. You will have an OSD for volume and display brightness setting information without lag and performance hit. The guide is fairly easy and only requires average computer knowledge.
1) Go to your ASUS ATK package location. Default is C:\Program Files (x86)\ASUS\ATK Package\ATKOSD2
2) backup ATKOSD2.exe (put it in an archive - zip or rar)
3) delete ATKOSD2.exe (if in use, End Task in Task Manager)
4) Go to C:\Program Files (x86)\ASUS\ATK Package\ATK Hotkey
5) copy ATKOSD.exe
6) Go to C:\Program Files (x86)\ASUS\ATK Package\ATKOSD2
7) paste ATKOSD.exe
😎 rename ATKOSD.exe to ATKOSD2.exe
9) Open ATKOSDMgr.exe from C:\Program Files (x86)\ASUS\ATK Package\ATKOSD2 and tick "Enable ASUS On-screen Display"
10) Restart and your 3D OSD will be replaced with 2D OSD!