That description is much better.
The issue is that the file names are not case sensitive in Windows 7, so whether it's all capitalized or lower case, Windows 7 sees the name as the same so it doesn't think you are actually renaming it.
To workaround this, rename it to Acronis1
, then rename it again to ACRONIS
so Windows 7 will see it as an actual change and allow it.
Hope this helps,