Windows doesn't boot anymore after partition change

Background: I normally use Linux as OS. I had a dual boot with Windows XP. Since I had some problems with the windows partition (too long to explain), I shifted it of a while. This is what I have done:

1. resized the filesystem with ntfsresize -s idontrememberthenewsize /dev/sda3
2. rebooted the system and checked that windows boots normally
3. backed up the partition with dd if=/dev/sda3 of=~/win.img

4. using fdisk, I deleted the old partition and recreated it, restoring its id and boot flag. Now windows partition is /dev/sda8:

   $ fdisk -l
   
   Disk /dev/sda: 2000.4 GB, 2000398934016 bytes
   255 heads, 63 sectors/track, 243201 cylinders, total 3907029168 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 4096 bytes
   I/O size (minimum/optimal): 4096 bytes / 4096 bytes
   Disk identifier: 0x000da6c5
   
      Device Boot      Start         End      Blocks   Id  System
   /dev/sda1            2048      616447      307200   83  Linux
   /dev/sda2          616448  3907028991  1953206272    5  Extended
   /dev/sda5          618496    17395711     8388608   82  Linux swap / Solaris
   /dev/sda6        17397760    78837759    30720000   83  Linux
   /dev/sda7        78839808  3702228991  1811694592   83  Linux
   /dev/sda8   *  3702231040  3907028991   102398976    7  HPFS/NTFS/exFAT
   

5. restored the partition image with dd if=~/win.img of=/dev/sda8

6. sudo update-grub
7. changed the partition number to "5" in the boot.ini file of the windows partition (read here for more info)

I also tried other partition numbers, from 1 to 8, but nothing. Only a black screen with the blinking text cursor at top-left is displayed.