I found this hack for my LG HT321 and it works! It's pretty simple, just follow the instructions carefully. This info came from a post that I found for a different model, but it works for the HT300's so I changed the model numbers in the instructions.
Here's how to do it.
"No Disc" shown on the screen,(i.e. turn player on without a disc) type in on remote Pause 1472
A screen will come up with PROM SETTINGS
Press up on remote til you reach 05 Xe, where X is a number eg 2e.
Type 0, then hold 5 for a few secs then release, so it shows as 05 0e, press enter.
Press up til you get to 07 xx, where xx is 02 on mine, and press pause. (On my HT321 itīs not 02 but e8,
but it worls just the same!)
Turn system off, then on again.
Your LG should now be region free.
IMPORTANT: DO NOT adjust any other numbers, as this can cause damage to your system!
The screen shown above is essentially the BIOS settings, so any changes are permenant unless you do the same routine. Not even the system reset will work!
IF IN DOUBT, DO NOT TOUCH! WRITE DOWN THE NUMBERS BEFORE ADJUSTING IN CASE IT GOES WRONG! May also work on other players. This way is at your risk, and i will not be held liable if it does not work on your player!