ubuntu 12.04 installer does not recognize drive partitions

When the installer gives you the selection to install grub to /dev/sda only, that's normal. You see, in Linux, partitions and disks are represented this way:

• Disks are represented as an entry in /dev with no number at the end. sdas are SATA disks, hdas are PATA disks (CD drives are usually cdrom, cd, cdrw. Same for DVDs).
• Partitions, however, are represented as the device they are on (the above point) followed by a number. So, while /dev/sda is your disk, /dev/sda1 is a partition on that disk.

The boot loader doesn't install to a partition -- it installs to a disk. That's why the install is asking whether you want to install on /dev/sda, which is a disk.

I was having an identical problem also on an HP Pavilion machine. I booted Ubuntu from CD and wanted to move to a permanent installation (not trying to create a dual boot machine, actually, a pure Linux box). I created all of the partitions with GParted but the installation tool didn't see them. Interesting bit is that fdisk -l did not see the partitions either.

The fix was to run sudo dmraid -rE . Once that was done, the installation tool saw the hard disk.

In my case (Arthur Borsboom) this fix removes something related to Nvidia RAID (nvraid), which I have been using in the past for Windows.