Stemming up from a few Xbox tech sources is a claim from the Xboxhacker (XBH) Forums stating that the Xbox 360's DVD key and game region code can be altered to break down the region locks for some games. And following that particular tip by XBH member Seventhson, a flurry of third-party experimentations are beginning to back the claim in its entirety.
"I successfully changed the DVD key and region code of a 360. So it's all confirmed. ... All I did towards this was to reverse the plaintext KV signature to figure out how to modify and resign the KV contents," said Seventhson in his post, assuring that he isn't here to claim fame for this find.
He has stated that this triumph was built upon works of other Xbox hackers and wishes to thank four others - Takires, TheSpecialist, Robinsod, tmbinc - for their region code tests and SHA1/RC5 documentation. But it appears that the patch only works for some versions of Xbox 360s, which include all those with exploitable Hypervisors (kernels 4532 and 4548).
Meanwhile, one other Xboxhacker contributor going by the name of Arakon has successfully loaded a region-locked game, stating, "My USA 360 just booted a PAL (non-region-free) game. The region patching works."
The following assumes you have the correct 1BL key and CPU key set in the flashtool. 1. Dump the NAND from the US 360 (528-bytes-per-page) 2. Open in the latest flashtool (v0.8) and click [extract] 3. Edit extracted KV.bin and change 16-bits at offset 0xB8 from 0x00FF to 0x02FE 4. Open in flashtool and click [patch], check the "patch keyvault" box and select the KV.bin modified in step 3 5. Click [OK] and choose output file 6. Flash output image back to the NAND of the US 360 7. Try an EU game or two.