|"I tried to change the font size and this also, doesn't work"|
Are you trying to change the Send font size or how it appears on the screen?
Is this the procedure you are using:
As for the screen, holding the Ctrl key and rotating the mouse wheel should (in theory) do it.
I can't think of anything more to suggest about your read/unread issue other than that given in the link at #3. Clearing Temporary Internet Files and registering the files are easy to try and pose no risk.
Always pop back and let us know the outcome - thanks