iMAC can't boot to Mac or Recovery HD or Installation DVD
Guys, need some help here, I have been struggling with this problem for weeks. Worked with Apple Care, Apple service center. but the problem came back again. Now I just want to reinstall the system by my self.
HW info: IMAC 21.5 inch , CPU Intel i5, RAM 4G, Graphic Card, AMD 6700M
System info: Lion 10.7.2, Win 7 home edition, Bootcamp 3.2 (probably), Got 4 logic Hard disk, (1 MAC, 1 BootCamp 2 NTFS windows disks)
Issue history: Worked fine in both Lion and Win 7. One day in Win7, display got distorted and system hang. Reboot the iMAC, can't get in MAC, recovery HD or safe mode of MAC (Holding shift key when boot up). Ended up in a white screen. Can get in the Win7, but can only work on defaule VGA graphic card driver, if install the AMD 6700 driver, system gets hang sooner or later.
Trouble shooting steps:
Tried following steps, all ended up in a white screen:
1. reboot holding shift key to safe mode
2. Reboot holding command+option+R to recovery mode
3. Reboot holding option goes to recovery HD.
4, Get a Lion installation DVD from internet, hold "C" during reboot.
5. Unplug the power cord for several hours and reboot again.
Tried resetting PRAM (hold command+option+P+R) but no help.
Sent the iMAC to Apple support center, the engineer there tied to reset the PRAM again and they secussefully get in the MAC, they tested the hardware and everything seems fine. But issue happened again two days later.
I am trying to reinstall Lion by myself, but I can't get in to the installation page till now, neither for the recovery mode. Any suggestion to get this done? Thank you so much for your help.
iMac, Mac OS X (10.7.2)