Windows ties the boot style of the computer to the partition table type:
The error message you received indicates that you're violating this rule: You've booted the installer in BIOS mode, but the disk uses GPT. There are two ways around this problem: change the boot style or change the partition table.
Changing the boot style will enable you to install Windows on the hard disk without changing the partition scheme. Since changing the partition scheme could be difficult, this approach has a certain appeal; however, it may not be possible. To boot in EFI mode, your firmware must support EFI. Most computers sold since mid-2011 do support EFI, so if your computer is recent, this may be an option. If your computer is older than this, though, the odds of it supporting EFI drop greatly. If you think your computer is EFI-capable, you'll need to find a way of booting the Windows installer in EFI mode. This can often be accomplished via the firmware's own boot manager (the same tool that lets you select to boot from an external medium on a one-time basis). Typically, you'll see two options in the boot manager, one of which mentions "EFI" or "UEFI" and the other of which doesn't. Select the EFI/UEFI option to boot in EFI mode. Other times you may need to change an option in the firmware's setup utility.
If you change the boot style for Windows, you may need to do so for Linux, too -- although it's possible that Linux is already booting in EFI mode. Look for a directory called
/sys/firmware/efi -- if it's present, you're booting in EFI mode. If not, you're probably booting in BIOS mode. If you want to switch modes, you can install any EFI boot loader you like. See my Web page on the topic for an extended report of the options and procedures.
If your firmware doesn't support EFI, then your best option is to convert the disk from GPT to MBR. You might even want to do this if your firmware does support EFI but you're currently booting Linux in BIOS mode, since then you won't have to deal with unfamiliar EFI boot loaders for Linux. You can do this conversion with my GPT fdisk (
gdisk) utility (which is part of the
gdisk package in Ubuntu), albeit with some caveats concerning the number and placement of partitions. Specifically, if you have more than four partitions, some of them will have to become logical partitions when converted, and each of these requires at least one empty sector between itself and the preceding partition. Thus, you may need to resize some partitions, carving a tiny bit off of their ends. (Resize the ends of the partitions that precede the to-be-logical partitions, not the starts of the to-be-logical partitions!) Also, after making the change, you'll need to re-install your Linux boot loader. Once this is done, Windows should install happily, provided you've ensured that the to-be-Windows partition is a primary partition rather than a logical partition.