Screen unresponsive ! HELP NEEDED

Are you running Windows 8?

All-in-one Touch-screen Functionality Lost After Windows 8 Upgrade

if its been water damaged or anything like that to where the screen is even cracked or scratched touch phones are very sensitive and yes it might need to be replaced.

same thing happens to me - most of the time it will just randomly freeze; occasionally i get an unresponsive black screen. this 24' aluminum imac usually has startup problems also - sometimes it will "gong" and nothing else; sometimes the apple logo will come up and then nothing else; sometimes it will load the logo and then spin for a few seconds and then freeze - the only option is to manually shut down. there is no rhyme or reason to it

Start by logging on as the Administrator so you can check the Task Manager and find out what Application or Process is monopolizing the system.

If the system is still unresponsive boot into Safe Mode. (Press F8 before the Windows startup screen appears.) If everything is fine in Safe Mode type MSCONFIG at the Command Prompt and start disabling features until you find the culprit.

Last resort, buy or borrow an external USB CD/DVD drive and use it to reinstall Windows.

Important: Reinstalling will ERASE the hard drive.

If this helps please vote for my solution.

One of your programs (or drivers) that is set to run at startup is corrupted. Stop them from loading one by one until the problem is fixed and uninstall (or update) the culprit.

get a new one or go to fixphonenow.com

Sounds like your is overheating. You might want to make sure your CPU fan is spinning. Another good thing you can do is download a little program called speedfan http://www.filehippo.com/download_speedfan/
this will tell you the internal temp of your processor and hard drives and if your fans are running. If the fans are running and the cpu is staying cool, I would then do a full bios test on the hard drive itself as well as a chkdsk /x through a command prompt on the hard drive (from safe mode). Let me know if these don't resolve the issue.

It is possible the power supply is now too small for the number of loads you now have.Not sure what your CPU is ,but I bet it is 80 watts just by itself. The minimum wattage requirement or the video card by itself is 300 watts.Add the drives,ram,fans and mobo and you way underpowered.

sounds like you have board problems.
unplug everything from it first and see if this helps could be something you have plugged up could be bad too.
you will have to open box and look for damage and then one by one unplug something and then reboot to see what it might be.