[mark_k]

Originally Posted by Sim085

I found a lot of instance when searching for the above. I attached a screenshot as I am not sure if all entries are relevant. I see CrossDOS, MS-DOS etc... (01.png).

The only possibly-relevant entries are where the DOS string begins on a 512-byte boundary as Thomas said.

Did you also search for 44 4F 53 03 00 00 00 00 00 00? That's the international FFS partition type/ID. Your lost partitions may well be of that type if you used HDToolBox's default options. You can add more zeros to that search string if you want, since you're searching for a 512-byte block where all except the first 4 bytes are zero.

I also did a quick search for 44 4F 53 01 00 00 00 and I found five instance of this in the image file at the following lines:

0007e000
003f0400
le94cc00
5a373a00
6c3ec00

Now I just have a question and I promise this is one of the last ones before giving up; How do I determine Cyl (for LowCyl and HighCyl) from the line numbers? Or it is not something that strait forward?

It is fairly straightforward. And don't give up, just when you might be getting somewhere.

Now the 44 4F 53 01 signature is for a standard FFS (non-international) partition. That might be a remnant from when you partitioned the card differently in the past. So this isn't necessarily the start of the partition you want to find, but...

I'll start with the $7E000 one. That's a likely start-of-partition point since it's near the beginning of the CF card. Check again there, are the rest of the bytes (to offset $7E1FF) all zero?

$7E000 hex is sector $3F0 = 1008 (you divide $7E000 by 512 to get the sector number).

If that is the start of a partition, because it starts on a cylinder boundary that suggests there are 1008 or maybe 504 sectors per cylinder (for the partition to start at cylinder 1 or 2).

In summary, to continue working on this I'd suggest:
- Try to remember your previous partition layout. Are you certain what filesystem type the partitions used (FFS or FFS international)? Roughly how big was each partition?
- Also search for 44 4F 53 03 00 00 00 00 00 00 00 00 00 00 00
- Note down the positions where that string appears. Only ones with positions a multiple of 512 are relevant.
- If you remember roughly how large each partition was, that can help narrow the possibilities down further. For example if your first partition was about 500MB, then the start of the 2nd partition will be about 500MB into the image file. So concentrate on any search matches around there.