I have an HP Pavilion 17 with Windows 8.1. Hated Win. 8.1 so installed Win. 7 Ultimate. I ended up with a bad key for Ultimate so wanted to try Ubuntu. Like an idiot, I went over the top of 7 with Ubuntu 13.04. All was fine, but where we live I have a u.s. cellular usb modem for internet access. When I plug in the usb modem nothing happens. Nothing at all. So no internet for me. Which is really why I use the laptop anyway. I wanted to give up and just re-install my good copy of Win. 7 Home Premium-but when I got to the partition to install it on, it said I could not install it on that partition. So I deleted the partition and now have un-allocated space, but it still won't let me install 7. The error says this: Windows cannot be installed to this disk. It has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks. Really? 7 was it previously with no problem. Ideas to resolve this problem? Thanks, Linda