Partitioning error of installing f16 on a ubuntu-win7 dual-boot machine

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A HP machine with Win7 pre-installed, and I have installed ubuntu using half of the space (so dual-booted).

Yesterday I started to use the F16 x64 DVD to overwrite the ubuntu. Every time I tried it stopped with a partitioning error: you have not created a bootloader stage 1 target device; sda6 must have one of the following disklabel types: gpt.

I have tried the following options:

1: in partitioning options, choose "remove existing linux partitions", and failed with the error;

2: customized partition layout, and created both /boot/efi and /boot, and failed with the error;

3: start the installation session with "nogpt" kernel option, and repeated the above 2 options, and failed with the error.

I have checked the partition type and it turns out to be msdos. Currently the dual boot is done by grub. However I noticed that in my bios there is an option of "run uefi application..."

Here is the partition layout:

Model: ATA ST31000524AS (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
1 1049kB 106MB 105MB primary ntfs boot
2 106MB 494GB 494GB primary ntfs
4 494GB 988GB 494GB extended
5 494GB 979GB 485GB logical ext4
6 979GB 988GB 9260MB logical linux-swap(v1)
3 988GB 1000GB 12.1GB primary ntfs

And I have to keep the win7 partition, so clean installation is not an option...

So, anyone can give me some advice on how to process the F16 installation? Thanks in advance!!!