Please note that, this is not official release from HTC, The GSM Version, not Sprint CDMA version HTC Hero.  it's an Android Open Source Project by cyanogenmod.  CyanogenMod 6 is a free, community built distribution of Android 2.2 which greatly extends the capabilities of your phone.

This is an alpha preview and unsupported version. You have to know what you are doing when using this. If you don't, don't use it. If you do, use it at your own risk. You've been warned!

INSTRUCTIONS:

• - First time flashing CM to your Hero (or coming from another ROM)?
• 1. Unlock your device and install Amon_RA's recovery image
• 2. Do a Nandroid backup!
• 3. Update your radio if necessary
• 4. WIPE
• 5. Install the ROM
• 5. Optionally install the Google Addon

Source: cyanogenmod