Specifically with PowerShell, I have long used the following one line expressions to convert between the two formats. Just paste in your GUID or assoc and run the command. It will spit out the other representation.

GUIDToAssoc

[System.BitConverter]::ToString([System.GUID]::Parse('{D23929BD-D8F7-4411-75A0-BCD5F535E61B}').ToByteArray()).toLower() -replace '-'

AssocToGUID

([system.guid][byte[]]('bd2939d2f7d8114475a0bcd5f535e61b' -split '(..)' | ?{ $_} | %{[System.Convert]::ToByte($_,16)})).ToString().toUpper()

Technically, I believe Microsoft refers to the Assoc format as a "Packed GUID".

You can find complex descriptions of how to visually convert between Original GUID and packed GUID. These are generally not necesary.

However, it is just an alternate (and slightly more compact) string representation of the byte array that is used internally to represent a GUID in the operating system. I believe it started being used when the Windows registry was first introduced as it offered a more efficient way to store, sort and visually represent GUIDs within registry entries.

Note: In the windows application deployment world, there is another concept called "Compressed GUID" which is even shorter at 23 characters long. That is something completely different. It came much later and is not really used anywhere outside of application packaging to my knowledge..

You my friend, are a HERO!

Thank you!