ubuntu appears in BIOS menu (UEFI)

What you see is the a UEFI BIOS. Unlike the legacy BIOS, there's MBR where the bootloaders always try to overwrite each other. Instead, bootloaders are installed in the form:

<EFI system partition>/efi/{vendor}/{file}.efi

The EFI partition is a small, FAT32 formatted partition usually located at the beginning of the hard drive. It stores the bootloaders for all the UEFI compatible operating systems you have installed.

Once a UEFI compatible operating system is installed, it copies the bootloader to the EFI partition and creates an entry in the NVRAM which points to the bootloader. In your case, ubuntu points to

<EFI system partition>/efi/ubuntu/grubx64.efi

Windows, for example, creates an entry called "Windows Boot Manager" pointing to

<EFI system partition>/efi/microsoft/bootmgrw.efi

---

So, with a UEFI BIOS, you can use its boot menu to select your operating systems, set the default operating system to boot, etc.

Also, Ubuntu 11.04's installer has a bug where it will reformat your EFI partition. So, if you have Windows installed, it will no longer boot. You'll have to install Ubuntu first, then Windows.

EDIT: One more thing :) If you want Windows to show up in the boot menu, you have to boot the install DVD in UEFI mode. There should be an option for that if you look in your BIOS settings.

Hope this helps