partition problem

I accidently zeroed out the first sector of the sda drive I had was going to wipe grub but forgot about the partition table needing to stay! I had an extended partition and 15 logical partitions in the drive (/dev/sda) Now my drive shows up as unallocated. I want to beable to recover this drive. I have tried part and gpart -W /dev/sda /dev/sda But it didn't help (it does show the extended partition but when I tried to recover it did not work). I am sure that nothing else other then the first sector was damaged/written to before I use these tools. I am in the process of trying testdisk and searching deep. The extended and all it's logical drives are ext4. If these tools don't work is their any way to manual search for the beginng of an ext4 partition. For example ntfs filesystems you can dd if=/dev/sdx/ | grep -a "NTFS" because each ntfs drive starts with the label NTFS on it's first partition sector (begining of filesystem). Not sure if their is a delimiter for ext2,3,4 Also not sure if these software utilities like part , gpart , testdisk ,..etc support recovering ext4? (I know they say ext2/3 but 4?) Thanks for any help At the very least I would like to recover the 10th partition in the extended partition file /var/lib/tomcat6/webapps

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