I am trying to install Ubuntu 11.10 in a dual boot with my existing Windows 7 but the installer does not detect any existing partitions.

I have tried resetting my BCD using EasyBCD and doing fixmbr from the Windows startup disc. A while ago I had to use TestDisk to recover my partition table so this might be the cause but I have installed Ubuntu and Windows many times before with no problems.

fdisk -l output:

Disk /dev/sda: 640.1 GB, 640135028736 bytes
255 heads, 63 sectors/track, 77825 cylinders, total 1250263728 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x360555e5

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048  1250274689   625136321    7  HPFS/NTFS/exFAT

Disk /dev/sdf: 7803 MB, 7803174912 bytes
255 heads, 63 sectors/track, 948 cylinders, total 15240576 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x6f795a8d

   Device Boot      Start         End      Blocks   Id  System
/dev/sdf1   *          63    15240575     7620256+   c  W95 FAT32 (LBA)