I’ve been switched to Twitter mobile (which I detest) presumably because I have IE 6.0 or 7.0 however, my computer indicates that I am currently running IE 9.0 with Windows 7.0. What do I need to do to fix this issue and switch the Twitter app on my PC back to what it used to be?

Are there any special settings you’ve made to IE9 that may cause websites to consider it an older browser?

Try this: From Menu Bar, selct Tools > Compatibility View Settings. If “Twitter” is listed, remove. Close your browser and try Twitter again.