When i ordered the hard drive, i also ordered the start up disks, there are 4 disks one system disk and 3 disks that have all the data the system came with. the system disk is 1 of 1 and the other three are labeled 1 of 3, 2 of 3, and 3 of 3. After i put the hard drive and the disk drive in I turned it on the blue lite on the power button lit up and the lights on the front lit up the fan came on but no screen just black. I pulled the Ram chips, and only put one back in, putting it in the opposite slot , closest to the board. Hit the power button and the screen lit up, it was still black with the start up program posting, ending with operating system not found.when i put the other ram chip in the unit does not post anything, the screen stays black. I can open the bios,In the bios i put the CD/DVD on top to boot first, I put the system disk in it and restarted it, I got the same screen, that ended with operating system not found. I went into the bios and disabled the networking line that allowed the system to go to the network to find the start up data. When i rebooted it one line came up Missing the operating system.I tried restarting it several times with the system disk, still the same prompt operating system not found. I went back into the bios and enabled the network line s and restarted it several more time and still operating system not found. I tried the ISO image Acer said to use, I burned it onto a CD from acer download, I also put the ISO image on a flash drive, to try that still the same post ,Operating system not found. I had ordered another system start up disk, 1 of 1, still the same prompt. I put my ear up to the hard drive to see if it is running I could hear it churning I can not hear the disk drive spin, it does have the disks spinning slow when I eject the disk. Here is the information It is an Acer Aspire 7741z 4433, it is to have windows 7, I was told when I ordered the disks the Operating system is on them,. I also tried to load my Windows XP professional Operating system, It would not load that either, it just posted the same thing operating system not found. I have disassembled the unit several times, I removed the CPU to see if it were damaged, it was not, everything looks fine, all the connections are good. I am going to Google imgburn as you put in your post. From what I gather from your post The darn thing should take the system disk and the following three disks, right onto the new hard drive. One more thing I put a 7200 RPM hard drive into it, instead of the 5400 RPM I hope that is not the problem. Let me thank you for responding to my call for help, I will let you know if the imgburn works, thanks again and have a good thanksgiving.