Thanks for the reply. This set is a DLP set and has several moving parts inside, the Fans and the Color Wheel. Typically, the Color wheel screeching, or failing would lead to a distorted picture or no picture. The fans, so long as they are spinning and keeping the TV from going into Thermal Protect, will continue to work and the picture would be just fine.
Commonly a build up of dust and dirt will cause friction in the fans, and can cause grinding, squeeking or screeching noises like the one you've described. A possible solution would be to disassemble the fans by rmeoving the rear panel of the TV, then cleaning and lubricating them with WD-40, or possible replacing the fans.
Are you comfortable disassembling the TV and poking around to clean the fans out?
If not, then you could locate a technician at the link below and have them perform this work for you:
If you need further assistance, let me know.