I had this idea for quite some while now and I believe it's doable... After learning how the MEGA-CD works I started to read about how the region protection mechanism works on this system and found out that achieving real region free is possible somehow. For a long time I've been patching my games to run on a JP/Asia MEGA-CD by doing this on the ISO images: - Extract header using Winhex - Manually edit the header to match the strings the Japanese ROM expect - Paste the Japanese security program on top of the original (US or PAL) security program -Pad the difference with 68000 NOP instructions. The success rate with this method has been 100% so far. But using the real silver discs is much more desirable than using shitty CD-Rs making real free region interesting. The security checking is done by the SUB-CPU during the second part of the disc detection process (when the CPU reads the TOC information from the CD Drive) where the security program is compared to an existing copy of it on the SUB-CPU RAM. The idea is change the compare code to instead, copy the loaded security program that would be used on the compare on top of the original security program which came from the disc read then pad the size difference with NOP instructions automatically. This would cause the Japanese ROM to behave as a region free ROM. Then why it has to be the Japanese ROM ? Because it's security program is the smallest of the 3. What you guys think of this idea ? I'm not capable of doing it alone because the ROM has the SUB-CPU BIOS image compressed on the main 68000 ROM chip. Decompressed it's 128KB just like the main ROM image. I would need help reverse engineering this, changing it and then putting it back onto the ROM. :shrug: Edit: Achieved. Link: http://www.4shared.com/file/0HXCyFYT/Hacked_MEGACD_BIOSES.html Package contains: eu_mcd1_9210_regionfree.bin EU_MegaCD2_30031993_regionfree.BIN jp_mcd1_911228_region_free.bin JP_MegaCD2_22121992_regionfree.bin JP_Wondermega_02061992_regionfree.BIN us_scd1_9210_regionfree.bin US_SEGA_CDX_930907_regionfree.bin US_X'EYE_27121993_regionfree.bin Edit: Added a utility to byteswap the BIOSes on this post. :thumbsup: Usage: Name file "BIOS.BIN" and put on same folder as .exe and .bat... Click .bat and a file named "SWAP.BIN" will be created. Edit2: Unified link. Contains all files.