I am working on a Acer Aspire 4720z. Won't boot. Windows Error Recovery won't work. Launch Startup Repair just returns to same screen, Start Windows Normally goes to black screen and hangs. Will not boot from CD/DVD. Have tried Vista CD and Win 7 DVD. Do not have recovery disks. Have been trying to use flash drive to somehow get to CMD promt to do clean install but unsuccessful. Will not go to any safe mode. Any Ideas? Acer will not help without paying for it. Has Vista Home Basic installed I believe. I know it's Vista but unsure on version.