Edit - Super User

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Recovering a Windows XP License key

I threw out a Windows XP machine a while ago (the motherboard failed). I kept the hard drive and the XP installation media.

Problem is the license key was on a sticker on the machine - doh! The original manufacturer has gone bust (Evesham) and I suspect that Microsoft will be of little help.

Is there any easy way to get the license key off the hard disk? Can I just find the file with the registry data in it and get the key using a hex editor?

I really need a spare XP key for use in a Windows VM.

Answer

If you are able to extract the 15 bytes from positions `0x34` and `0x52` (52-66) in the `DigitalProductId` Registry Value as a Hex string, you can use the following Python (Python 3) script to convert the bytes to a Product Key:

    import sys
    
    def eprint(s, *args, **kwargs):
    	sys.stderr.write(s.format(*args, **kwargs) + '\n')
    
    class KeyConv(object):
    	_alphabet = 'BCDFGHJKMPQRTVWXY2346789'
    	def __init__(self, val, verbose = False):
    		self._val = val
    		self._verbose = verbose
    
    	@classmethod
    	def _int_to_indices(cls, val):
    		while (val > 0):
    			yield (val % len(cls._alphabet))
    			val = val // len(cls._alphabet)
    
    	@property
    	def key(self):
    		a_idx = list(self._int_to_indices(self._val))
    		s_key = ''
    		for i in range(0, (25 - len(a_idx))):
    			s_key = s_key + self._alphabet[0]
    		for idx in reversed(a_idx):
    			s_key = s_key + self._alphabet[idx]
    
    		if len(s_key) != 25:
    			if self._verbose:
    				eprint('Invalid Product Key length: {} ({}) from 0x{:X}'.format(len(s_key), s_key, self._val))
    			s_key = s_key[-25:]
    		chunks_key = (s_key[(5 * pos):((5 * pos) + 5)] for pos in range(0, 5))
    		return '-'.join(chunks_key)
    	@classmethod
    	def from_hex_string(cls, shex, *args, **kwargs):
    		return cls(int(shex, 16), *args, **kwargs)
    
    if __name__ == '__main__':
    	import argparse
    	parser = argparse.ArgumentParser(description="""Decode a Windows Registry value to the corresponding Product Key""")
    	parser.add_argument(dest='hexstring', help="""The hex string to decode (from the Registry)""", metavar='STRING')
    	parser.add_argument('-v', '--verbose', dest='verbose', action='store_true', help="""Output more information about conversion""")
    	args = parser.parse_args()
    	k = KeyConv.from_hex_string(''.join(args.hexstring.split()).replace(',', '').replace('\\', ''), args.verbose)
    	print(k.key)

Sample run:

    > python3 key-conv.py -v "A2 23 51 D0 2A 38 5D 22 C4 41 6B 87 43 C1 00"
    Invalid Product Key length: 27 (CDKHCQQBBCW2TT7QRF42M6V3YQY) from 0xA22351D02A385D22C4416B8743C100
    KHCQQ-BBCW2-TT7QR-F42M6-V3YQY

You can see the details about where to find the `DigitalProductId` Value in another answer, but essentially, look in the Registry Key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion

If you cannot access an interface to the machine, but can access the filesystem, find the Registry Hive at:

    %WinDir%\system32\config\software

If you are having trouble extracting the data, you can Export the `HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion` Key and then open the resulting `.reg` file. If I wanted to expand the script, I could add a Registry or `.reg` file extraction routine.

Edit Summary

Cancel

Add a comment |

Correct minor typos or mistakes
Clarify meaning without changing it
Add related resources or links
Always respect the author’s intent
Don’t use edits to reply to the author

create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
put returns between paragraphs
for linebreak add 2 spaces at end
_italic_ or **bold**
indent code by 4 spaces
backtick escapes `like _so_`
quote by placing > at start of line
to make links (use https whenever possible)
<https://example.com>
[example](https://example.com)
<a href="#">example</a>

formatting help »
answering help »