Unable to get gl context problem

Can anyone please help me? I’m using Windows NT 4.0, graphic card is GIGABYTE TNT2. A few weeks ago I may have accidently deleted some important dll or other files when I uninstalled some no longer used program. Now I cannot run any OpenGL program on my computer. Everytime when I try, it prompts “Fatal Error: Unable to get gl context!” or “wglCreateContext failed”. I have installed the Windows NT service pack 6a, but with no effect. Can anyone tell me how should I conduct a checking procedure to find out what is missing on my computer and how can I restore its ability to run OpenGL programs? Thank you very much!
(BTW this is very urgent because I am using Multigen Vega to develop some graphic applications. And now Vega cannot run because of this problem.)