I have an HP Pavilion PC with a 1.3 TB hard drive hosting Windows7 Professional. I have a couple external FAT32 format drives I use for backups as well. When I attempted to install Ubuntu 12.04 beside the existing OS, the only option I got was to put it on one of the external drives. If I went to the advanced options, it would show the internal drive. Any ideas why it won't let me install there?
I had a similar issue when going through the installer. I had to choose the advanced option to specify exactly how I wanted it to install, (specifically, to pick the internal HDD). Otherwise, it defaulted to my external HDD too... and I had no option to select my internal main HDD.
This is likely not a bug with your computer, but the new installer. If you need guidance on how to use the advanced option, I can help.
If you already have 4 primary partitions on your main hard drive, this could be the issue.
You can check this with the gparted utility that comes with Ubuntu, just boot the live CD, open terminal and execute:
Some computer manufacturer create multiple backup partitions to enable a system recovery. If this is the case, you can make a backup of a user partition, delete it and create a secondary partition.
You can create as multiple partitions on a secondary partition and ubuntu will install without problems.