You have to determine what files were changed by the mod. Then replace the offending files by re-installing the game or extracting the offending files from the CAB files found on your original discs. To figure out what files were installed, unzip the original file to a temporary folder. If just the global.iff file were changed then replacing it with the original should fix the problem.
You and any others should never install a mod without backing up the files first. To avoid this problem use the JoneSoft generic mod enabler. Leftos made a post in the NBA 2K12 section.
viewtopic.php?f=143&t=84240 If you use the JSGME you can not screw up the original installation but you can easily determine what mod caused the issue.