I have used older projects with Greek characters in ANSI and code pages without problems.
Indeed unicode will solve the problem, but this specific project is too big and I have to make too many changes to finally make it work fine.
Anyway, I managed to fix the problem changing the title of the title dynamically inside the code.
Take in mind that when I recall strings from the Resource String Table using CString.LoadString(ID) I get gibberish but when I am using CStringW.LoadString(ID) it works. My String Table is not Unicode but inside VS2008 I set it up as Greek code page.