Here's a quick guide how to change your Hero's MAC Address.
Changing MAC Address is legal, but check your local laws, just incase.
You will need the Unlocked SPL for GSM Hero to do this. Please click the link if you haven't already got it.
You'll also need the AndroidSDK and fastboot/adb drivers installed.
1) Open up a new command window.
fastboot oem rebootRUU
fastboot oem emapiWlanMac
... INFONotice: This MAC address takes effect only when your platfor INFOm is EEPRON-less configuration. Please use (emapiTest) to v INFOerify it ! INFO0x00000000 INFO0x000000DE INFO0x000000AD INFO0x000000BE INFO0x000000EF INFO0x00000000 INFO-eMapiWlanMacCommand, status = 1 OKAY [ 0.025s] finished. total time: 0.026s
7) Now, type this command to set the new MAC Address that you want (MAC Address should use spaces instead of ':'):
fastboot oem emapiWlanMac 00 01 02 03 04 05
8) Done! Type this to reboot:
fastboot oem boot