i have searched and serached, and have not found a clear answer that applies to this system...

i have a Dell Optiplex GX270, all default hardware
120 GB IDE HDD (replacing a 40GB IDE Drive)
80 GB IDE HDD (swapped in for Win 7 use...)

i had install iatkos 5i and iatkos v7 with no problems.
i ran the update to S3 V2 and used to be able to get into the install DVD.

NOW, my HDD with 10.5.8 failed and i wanted to try the nawcom USB retail install of 10.6 (by all accounts, the GX270 is compatable) nut that version hangs during install.. so i tried my old iAtkos V7 and now i only get up to IOATACONTROLLER Device Blocking Bus.
I tried with iAtkos 5i, V7, S3 V2, and the Nawcom Retail USB, but can no longer install Mac OS X... no i ran many diagnostics on the HDD, and it come up clean, no clicking noise, and even install xp, vista, and win7 with nmo problems. but ALL OSX86 projects have hung on the IOATACONTROLLER error.

i have read that it has to do with Hardware malfunction on the HDD, but this is a fairly new drive (6 months since i purchased)
i have also read that the driver during boot have to do with it, but the discs worked brfore, so why all of a sudden do they NOT want to work?

Please ANY help will be greatly appreciated...

System Specs are as follows:

Computer Model OptiPlex GX270
BIOS Vendor Dell Computer Corporation
BIOS Version DELL - 8
BIOS Date 06-26-06

Manufacture Intel(R) Pentium(R) 4 CPU 2.80GHz
Clock Speed 2.8GHz
L2 Cache Size 512

Memory Slot1[DIMM_A] 512MB
Memory Slot2[DIMM_B] 512MB

IDE ATA/ATAPI Controllers
ATA Channel 0
ATA Channel 1
Intel(R) 82801EB Ultra ATA Storage Controllers - 24DB
Intel(R) 82801EB Ultra ATA Storage Controllers - 24D1