Squares rather than text!

I have just downloaded Norton360 on to my Mums PC (Windows XP).   Strangely most of the text has come out as squares (I think it is Symbol Font).  I read somewhere that is a corrupted MS Sans Sherif font so deleted and downloaded a fresh MS Sans Sherif font but without  success.  Even the folder on desktop is labelled with 4 squares rather than NORTON.

Does anybody know how to resolve this issue please?

Thanks in advance for any help 

Adrian