Ubuntu 12.04 installer doesn't detect Windows partitions, but I can see them in "Try Ubuntu"

Chances are you've got one of two issues:

• A disk that uses motherboard-based software RAID (aka "fake RAID") and no appropriate software running in the Ubuntu installer; or leftover RAID data that's confusing the installer. You may be able to fix this problem by disabling RAID options in your firmware and/or typing sudo dmraid -Er /dev/sda in a Linux Terminal window. Note that this fix is risky; if the computer relies on RAID to boot and you remove the RAID data, you may no longer be able to boot.
• A damaged partition table. Your disk uses the GUID Partition Table (GPT) so fdisk will be useless for repairing it. Instead, use gdisk; see the gdisk page on repairing partition table damage for more on this topic. If you need more advice on this, post back with some basic gdisk output, such as the output you see when you launch it, type p, and type v.