Whenever I want to create a new text file using Windows 7 Explorer’s New ⇨ Text File context-menu entry, I get a file with an uppercase extension. For example instead of New Text Document.txt, I get New Text Document.TXT.
I searched HKEY_CLASSES_ROOT and found a key named .TXT. I renamed it to .txt and after rebooting, it works as expected. Unfortunately, after a while, it started happening again.
HKCR\.txtgets changed back toHKCR\.TXTor just the symptom (i.e., it is still\.txt, but new files have uppercase extensions)? Did you try monitor register writes? – Synetech Dec 02 '12 at 05:34