Imac started to slow down, then stopped booting. All I get is blank white screen. Took it to apple genius bar and they said I needed new hard drive, about $250 to fix. I took it for a 2nd opinion at a local shop, and they said I needed a new motherboard, about $800 to fix. So now I'm stumped. How can 2 reputable places say 2 different things? How can I figure out the real problem? I would like to get this fixed, as I have 0 working computers right now and I sell online so its imperative that I have one that works. I appreciate any help! Thank you!!
Googling "iMac white screen", it seems that this problem is commonly disk related. And, let's face it, disks fail more frequently than motherboards - they even just get corrupted sometimes. And things gradually getting worse - as you report - rather than suddenly is more typical of a disk problem.
Things you could try are:
1. Reset PRAM and/or SMC (Google if you don't know how).
2. Boot from your installation CD (if you can it's almost certainly not the m/b).
3. Use disk utility to check disk and repair permissions.
If none of that solves the problem then take it to the Apple Store and ask them to repair it, setting a maximum you are prepared to pay (say $300).
I say the Apple Store, not the local shop because:
1. They gave you the cheaper quote. $250 is not an unreasonable quote to replace the disk.
2. They know more about Macs than the local store.
3. They have the right equipment.
4. They have easier access to spare parts.
5. If it turns out to be a m/b failure they might even replace it for free as a goodwill gesture; 4 years isn't that old for a m/b (though it is for a hard disk).