Debian – Recover lost partitions ( or partition table) after fdisk in debian

I am running Debian Squeeze in my laptop. I did a big mistake. Instead of doing fdisk /dev/sdb (which is my usb pendrive), I fdisk-ed /dev/sda, which is my primary hdd.
When prompted, I chose options o and w and the reboot my machine.

Now, I cannot start my machine as it says no OS found.

Is it that, all my data is lost or only the partition table? How do we recover the data?

Edit:-
Initially I had 5 partitions. The partitions are as follows:-
A 105 GB for Windows installation, a 170 GB for storing data (possible NTFS), another 170 GB (possibly NTFS), a 1 GB (swap space) and 20 GB (ext4 partition). I was having a debian squeeze and win 7 dual boot.

105 GB
170 GB
170 GB
1 GB
20 GB

After loading an Ubuntu live cd, when I tried to see whether any partition structure exist using the Gpart command like,

sudo gpart /dev/sda

I got the following output:

ubuntu@ubuntu:~$ sudo gpart /dev/sda

Begin scan...
Possible partition(Windows NT/W2K FS), size(107419mb), offset(59139mb)
Possible partition(DOS FAT), size(2mb), offset(187738mb)
End scan.

Checking partitions...
Partition(OS/2 HPFS, NTFS, QNX or Advanced UNIX): primary 
Partition(Primary DOS with 12 bit FAT): primary 
Ok.

Guessed primary partition table:
Primary partition(1)
   type: 007(0x07)(OS/2 HPFS, NTFS, QNX or Advanced UNIX)
   size: 107419mb #s(219996159) s(121117248-341113406)
   chs:  (1023/254/63)-(1023/254/63)d (7539/51/1)-(21233/83/33)r

Primary partition(2)
   type: 001(0x01)(Primary DOS with 12 bit FAT)
   size: 2mb #s(4544) s(384488496-384493039)
   chs:  (1023/254/63)-(1023/254/63)d (23933/77/1)-(23933/149/8)r

Primary partition(3)
   type: 000(0x00)(unused)
   size: 0mb #s(0) s(0-0)
   chs:  (0/0/0)-(0/0/0)d (0/0/0)-(0/0/0)r

Primary partition(4)
   type: 000(0x00)(unused)
   size: 0mb #s(0) s(0-0)
   chs:  (0/0/0)-(0/0/0)d (0/0/0)-(0/0/0)r

ubuntu@ubuntu:~$

The screenshot is at

Shall I continue to write to the disk ? Does the partitions shown match my previous partitions as I mentioned ?