I did a really dumb thing. cfdisk threw an error at me saying "FATAL ERROR: Bad primary partition 3: Partition ends in the final partial cylinder", so I installed Partition Table Doctor to see if I could fix the problem. When the program started up, it told me there were problems with my partitions, and asked if I wanted them fixed (cannot remember real message, but I believe it had something to do with the cylinder boundaries), so, blindly, without thinking of the consequences, I did.

Now, my system will not boot. I tried booting from the Windows 7 installation CD. I went to install a fresh copy, but it said that "No drives were found". I then opened up diskpart. According to diskpart, there is only one partition, containing one volume, assigned the letter "C". Before, I had four partitions! It is also saying that the file system is RAW.

Is there any way I can fix this? I have important data that I do not want to lose.

Later on... I tried fdisk with the option -l, which lists the partition table(s), and this is what I got:

Ignoring extra extended partition 4

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 64 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x163df116

   Device Boot      Start         End      Blocks    Id  System
/dev/sda1               6          18      102400     7  HPFS/NTFS
Partition 1 does not end on cylinder boundary.
/dev/sda2              18        7851   62918572+     7  HPFS/NTFS
/dev/sda3           13073       30402   139196416     f  W95 Ext'd (LBA)
/dev/sda3           13073       30402   139196416     f  W95 Ext'd (LBA)
/dev/sda3           13073       30403   139203193     7  HPFS/NTFS

I don't know if this will help, but it's extra information, at least.

Also, this is how I had my partitions:

40MB (Unallocated)
100MB (System Reserved)
60GB (Windows, C:)
40GB (Was reserved for secondary OS)
~132GB (Home, E:)