Windows 7 HDMI output dosen't fit?

[NicolaiHelms]

Hi,

I used to just plug my HDMIcable into my computer with vista and then it all worked. When i do so now, my screen gets duplicated to my external LCD-tv, yes, but it dosent fill out the entire screen? It is just centered at the middle and i don't know what to do to make it fit?

Can anyone help?

Thx