Hello, from the things I can find MUI is.. by MSFT definition Multilingual User Interface
What is Multilingual User Interface Pack (MUI)?
Multilingual User Interface Pack is a set of language specific resource files that can be added to the English version of Windows Professional. When installed on the English version of Windows, MUI allows the user interface language of the operating system to be changed according to the preferences of individual users to one of the 33 supported languages. This allows large corporations to roll out the same worldwide image with a single install job. Local users can then select the user interface language or it can be set by Group Policy for Organizational Units.
MUI also allows different language users to share the same workstation or roaming users to take their localized user interface from one workstation to another. For instance, one user might choose to see system menus, dialogs and other text in Japanese, while another user logging onto the same system might prefer to see the corresponding text in French.
Some more interesting info here by inbfedsp
It also handles ,shell strings. That said, It was noted from all the things I read you DO NOT want to change anything here.
I would suggest as I do not have more knowledge on this is that you post a HiJackThis log and have the experts there determine if that is malware and how to safely get it out.
Please follow the instructions in this tutorial for posting a HijackThis Log. Preparation Guide for use before posting a HijackThis Log
After you have created it,post the log here HijackThis Logs and Malware Removal
and NOT in this topic,thanks.
Click on New Topic and copy/paste the entire log into the reply. Give it a relevant title,perhaps MUICache
Once you have posted the log DO NOT reply to it or change it until contacted or advised to do so by the HJT Team tech.
Should you have any other questions about this ask those here.