First, make sure your computer meets all minimum system requirements to run the game:
- Operating System: Windows XP / Windows Vista / Windows 7 / Windows 8 / Windows 8.1;
- Processor: Intel Pentium D or AMD Athlon 64 X2;
- Video Card: NVIDIA GeForce 6800 or ATI Radeon X1600 Pro (256 MB);
- Memory: 2 GB RAM (1 GB for Windows XP);
- Hard Disk Space: 25GB available space;
- Internet: Broadband Internet connection;
- Resolution: 1024 x 768.
If the requirements are fulfilled, navigate to C: > Program Files (x86) > World of Warcraft and rename the Cache, Interface and WTF folders to CacheOld, InterfaceOld, and WTFOld. After that, make show that you're able to see the hidden files and delete the Cache, Interface, and WTF folders from C: > Users > username > AppData > Local > VirtualStore > Program Files > World of Warcraft folder. If the problem persists, update your video card drivers, check for Windows updates and close all the programs running in the background. Also, make sure that your security program and Windows Firewall doesn't block the connection. If none of these solved the problem, uninstall and reinstall World of Warcraft.