Windows XP is the most common OS nowadays and is usually present in all the computers or laptops which range beween INR 18000 and INR 30000.But, even with the magnificent features on Windows XP don't seem to make most of us happy. Windows Vista is the 'in-thing' nowadays.But nowadays, almost nobody is prepared to spend INR 8000[approx.] on an OS. For this plain and simple reason,  themes for Windows Vista have been introduced,which dosen't change your OS from XP to Vista, but, changes it's appearence to make it resemble Vista.The only way to possibly detect whether you have an XP or a Vista is the loading screen when Windows boots up.A typical Windows XP would have the XP logo along with the signature-loading screen.