How may I get Explorer to preview .m3u files as text?

Start >> Regedit.exe

Find HKEY_CLASSES_ROOT\.m3u key and check the 'Default' setting (in my case VLC.m3u)

Find HKEY_CLASSES_ROOT\VLC.m3u (in this path substitute VLC.m3u with the value of your default setting in HKEY_CLASSES_ROOT\.m3u)

Create a new key in HKEY_CLASSES_ROOT\VLC.m3u: shellex

Then in HKEY_CLASSES_ROOT\VLC.m3u\shellex also a new key: {8895b1c6-b41f-4c1c-a562-0d564250836f}, so it should look like this:

The {8895b1c6-b41f-4c1c-a562-0d564250836f} key tells Windows that you want to use a preview handler, now you only should specify which one you want to use. Set HKEY_CLASSES_ROOT\VLC.m3u\{8895b1c6-b41f-4c1c-a562-0d564250836f} Default to this value: {1531d583-8375-4d3f-b5fb-d23bbd169f22} (text handler ID)

If you want to use other handlers in shell you can find their ID's in the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\PreviewHandlers