failing at "Try" choise on boot live

I have Zorin 8 on one system fine. Efforts to try 9 & 11 are failing (did not try 10). Loading .iso from dvd goes well untill reach Try / Install choise. Choosing "Try" yeilds persistant black screen and good mouse pointer, never to proceed from there. Can't even ctrl,alt, del out of lockup, have to press & hold pwr start button to bail out.
This is a Dell Dimension 8300, 32 bit machine, bios rev A07, ram=2.5Gig, Pentium4 @3.00 ghz, NVIDIA Geforce 2 GTS/Geforce2pro. Presently running Win XP in good order.
I am able to run live - other distros (MX15.1) being the most recent.
I could not find another report of this on this forum. Other first timers just assuming bad downloads and moving on? I did do the checksum bit when i downloaded as I had trouble with Zorin 9 as well. Should I just try to install?

When you see the boot screen, press F6 and select 'ACPI=OFF' and see if you get any further (with 9).