0. follow carefully this guide.
1. Charge battery to 100%
2. Remove SIM and SD
3. Disable antivirus
4. if you wish newer radio, then flash radio first (ap4 didn't contain any radio) (latest is 1.57 = x7510 radio. http://forum.xda-developers.com/showthread.php?t=372904)
5. it is better to do hard reset before flashing (Volume down + reset)
6. connect Athena to USB
7. go to bootloader (camera button (deep) + reset)
8. wait until windows installs driver (up to 5 minutes)
9. soft reset device and BOOT INTO WM!!
10. ensure your Athena and WDMC or ActiveSync are connected and no running such applications as MyMobiler or something that uses ActiveSync.
11. ensure that nothing syncronizes at this moment
12. unrar archive
13. launch exe, but ONLY ONCE!
14. wait while RUU opens (may take up to 10 minutes)
15. pray
16. then read carefully on-screen instructions and follow them.
17. when it will be flashed (if will be ok) do manual hard reset