Ive been running windows 7 for a while now, and decided to pull some data off of old hard drives. I plugged in one of my ata drives though a usb device and the disk management said it was an invalid disk. i tried taking it off line and bringing it back online and that just crashed disk management. I did have the option to convert it to a basic disk but that would wipe all data! So here’s what i did to fix it and keep my precious data!
First i downloaded HxD its a free Hex editor. once its installed open the problem disk by clicking “Extras” then “Open Disk” Make sure you open the right disk! your disk management will list your disks starting with 0, this tool will start with 1. this is very important as you could seriously fuck shit up if you don’t do this proper 
. Also, the default option is to open the disk read only, your going to want to uncheck that when your ready to fix your “Invalid disk”.
So we’ve got the broken disk open, scroll down to offset 1C0(the row) and look in the 02 column. that cell should read “42″ which means Dynamic disk, Change it to “07″ and save changes. if your using this drive externally unplug it and plug it back in. otherwise reboot your computer.
That should have re initialized the disk and it will now be readable. if not go into disk management and take the disk offline then bring it back online. and the best part No Data Loss!!! Hope this helps!
Update: Aaron Woffinden asked me to add how to fix a disk with multiple partitions.
how to fix a disk with multiple partitions SOLVED
1. once you correct: offset (the row) 1c0, column 02
2. directly below the row you just corrected (column “02″) are your other partitions
each row below row 1c0 is one of your partitions, and each should have a “42″ in column “02″
3. change each “42″ to “07″
Thank you!
