Windows user not administrator ??? Strange errors (1 reply)

Dear all,
I'm not a tech guy so I'm here to have some hints or help.
I did an installation of 3.1.3_x64 on a PC where run a PHP application and myslq db .
I used an administrator user i.e. admin to make installation. The icon of WS is green when I use this user.
This PC is within a hospital lan network and the internal security policy do not admit to have user with administrator grant level in any present PC.
They have created a normal netuser just to fulfill the company policy.
I created into mysql that user too with all priviledges just access to data.
When I login with this las1t netuser , wampserver runs on background, but , if I try to click on desktop icon then the small icon remains red. If I do refrest there are some errors about hosts... not possible to write...
Application run the same and data are recorded on db the same.

Now, after some time the browser stop with a error like that
(Fatal error: Call to undefined function mb_convert_encoding() in nm utf8.php on line 75) and the application stop to work.

Call to undefined function mb_convert_encoding()

I googled a bit but mb_string extension is active .... the installation was succesful .

I think is something more connected to the user than php setting..

Any help will be very appreciated.