I've had an NVIDIA Geforce 4 Ti 4600 for about two years and haven't had any hardware related problems with it until recently. The built-in fan failed, but it didn't effect performance until recently. Now, whenever I play a game that requires any 3d performance, such as Half-Life 2 or World of Warcraft, the screen will randomly flash off and on, the monitor saying that it has lost signal. This will happen for as short as 10 seconds or indefinitely, until I turn the game off and come back several hours later. There appears to be no rhyme or reason to the problem, as opening the case and blowing cold air into the card doesn't help. In certain cases, if I push it too hard and try to keep playing despite the random loss of signal, the computer itself will start to lock up, jamming in place for about two seconds before releasing. If it gets to this, it will keep doing it even when I'm on the desktop, making any music I play buzz loudly. I'm thinking that I'm going to have to buy a new card, but I'd rather not if I don't have to, as the Geforce 4 still works great on Doom 3 and Half-life 2.