How to copy "created" datestamp to "modified" of files - but not by hand?

[LyricsLover]

Using the file modification time is a really bad practice. I highly suggest you to change your process.

@Zerow

So does anyone know a way to automatically copy Created over Modified? And in a quick / easy way

Yes, in Powershell you get the various attributes and timestamps with:
$file = Get-Item C:\temp\YourFileName.mp3

then you got three timestamps:

$file.creationtime
$file.lastaccesstime
$file.lastwritetime

You can assign the timestamp .creationtime to a variable like
$MyCreationTime = $file.creationtime
and then assign the content of this variable back to your file with
$file.lastaccesstime = $MyCreationTime
or
$file.lastwritetime = $MyCreationTime

Now you have only to create a Powershell-Script which accept your selected files or do the above for the content of an entire folder or even recursive.

If you want to check the three timestamps, you can use:
Get-Item C:\temp\YourFileName.mp3 | select name, *time
If you want to check all the six timestamps (inluding the one in UTC), you can use:
Get-Item C:\temp\YourFileName.mp3 | select name, *time*