Well, you need to figure out exactly which 2008 model it is. If it's an Early 2008, then it sounds like your system is a candidate for the nVidia graphics chip recall program, which is a bonus for you because it's free if your system fails the diagnostic test. If it's a late 2008, then you're still likely looking at a bad video chip, but you're going to have to pay for it if you don't have some kind of extended warranty.
The quick and easy way to tell which model you have, is whether or not you have a unibody case. So if your laptop looks largely like the new MBPs, that's a unibody model and you're probably just going to want to buy a new laptop once you are quoted a price to fix that one. If it looks nothing like the current models, then you're probably in luck. Another quick way to check, is whether or not there's a button to press to release the display. No button means unibody.
If you have the non-unibody model, then take it to the nearest AASP shop or Apple retail store. They can run a special diagnostic program on it, and if it fails, and it sounds like yours will, they'll replace the logic board for free. Do not let them charge you anything for it, because Apple will pay them labor for the repair, and cover the cost of the part. If one AASP or Apple store doesn't know what you're talking about, move on to the next one. Think of it as a basic competency test. A good AASP would know about these extended repair programs, and have no problem testing for it. A bad AASP, or an unethical one, will either have no clue or try and double dip charging you on top of getting up to $99 off Apple for it. While Apple will claw back anything you pay to an unethical AASP, it's a hassle you don't need to go through. In fact, if an AASP tries to charge you for this, feel free to contact Apple and report it. They give the rest of us a bad rep.
I have a 2008 MBP 2ghz core 2 duo with 4 gig of non-apple ram. The problem occurred with an update and the machine refused to boot. It would boot until the apple and spinning gear but there were multiple images. Then it booted fine one time and I decided to try and get OSX Lion on to it but that didn't work - fuzzy multiple images stopped the machine and download. I've since installed OSX Lion onto a new 500gb hdd and installed that but to no avail. Still get the blurred startup images and failure to boot. Any ideas?

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