I have a 6yr old Sony VAIO laptop that will suddenly have the entire screen turn into a pixelated mess. This mess of a screen will stay that way until the laptop is restarted. It usually seems to happen when the machine is left idle for a few minutes. I don't think it has even happened while in use. I took the machine apart hoping to find a loose display connector or something and found nothing. I replaced the hard drive. The problem still persists. Any ideas? Thanks.
Try hooking up an external monitor. IF the pixelated mess shows up on both the laptop LCD panel and the external monitor then you know the panel is not the problem.
Download a temperature monitor (I like HWMONITOR by CPUID, free download, google it. Be careful to use the correct download button, not one of the ads that looks like a download button). Make sure your video/cpu/MB is in OK temp range, a 6 year old laptop can get a lot of dust and heat up. Heat can cause things to fail the way you describe.
Download a bootable diagnostic. (Google ultimate boot CD). Run the diag until you know that the pixelated mess shows up when you are booting the diagnostic disk. If it does then suspect hardware issues. If the dianostic works then it could be either HW or SW, but you should start by resintalling the latest video driver for your 6-year old laptop from the Sony Website (not from microsoft update).
Consider a new $300-$400 laptop. BestBuy has a ton of them. 6 years is a long life for laptops, and a modern $300 laptop will probably outperform even a high end 6 year old laptop.