Finally I bought new HDDs for my old Dell T7400. First I tried SSD 250GB (OCZ)...but failed to boot. I realized that AHCI mode somehow does not support boot up?? it was Ok before. In BIOS set up >> Drive, I changed to SATA then booting problem solved. So a people who hangs system in aswRvrt.sys during safe mode should check AHCI or SATA mode. Long story to short reinstalling Windows I change back to AHCI mode it was fine and no problem of booting.
I was trying to get my system back by window system image (F8 during boot or window 7 CD >> repair system >> from system image) it keep generated error ~~. Later I have found out I made system image from 1TB HDD. In window repair (Stupid ~~~) image from 1TB can not be recovered to 250 GB SSD although actual data is less than 250GB. So I purchased 2TB HDD then realized that mother board only recognize 1TB. so I split the HDD into two 1TB using my laptop USB port.
Finally my system image was restored back to normal. Thank you so much essexboy.
In summary When you have booting problem (Dell T7400)
1) check BIOS Drive setup ACHI to SATA
2) Check HDD fail (click of death -- Tick Tick)
3) Always make windows system back up image in USB drive
4) when you recover from it use a same size or bigger HDD.
Good luck on your trouble shooting~ I hope you all find right solutions in a seconds.
