What is the largest hard drive you can install in an imac before issues arise?

Hi,
I am having trouble with my 2008 24" imac.
I was told the hard drive was failing, so on a techs advice we installed new ram and a 2TB western digital hard drive.
At the same time he upgraded me to OSx.6.
Since then my computer goes to white screen when starting up 80% of the time without going to login screen.
If I unplug it and let it cool down it will start up on the second attempt usually.
It has been in for a comprehensive diagnostic and come back with a full pass on all the hardware.
It has been run through disk warrior and it was pulled up and fixed on a few issues, ran fine for 6 start ups at the workshop, but is still presenting the same issues when left plugged in here at home.
It does seem to be getting really hot, but when i left it on for 3 weeks for fear that it wouldn't start again, it didn't skip a beat.

Now I have narrowed it down to several things we are yet to try:
- Downgrading the hard drive to 1 or 1.5TB to see if the heat output is the problem.
- Installing a UPS to isolate the power to see if it is a problem with my house power supply.
- running another virus scan to see if we can detect anything.

Does anyone have any experience with this?
I am pulling my hair out here and really need this issue fixed so i don't have this constant interruption to my work.

Cheers
Annette

Welcome to the Mac Forums.

I'm not sure downgrading the hard drive is going to tell you anything. The 2 TB drive should be OK, however, if you would rather have a 1 or 1.5 TB drive that's fine.

Forget about the virus check, there are no viruses for the Mac and using an UPS is OK but I don't believe it will make a difference. The white screen of death symptom can be related to many things as a Google search will show.

When you start your iMac make sure you have nothing else attached to it such as an external hard drive. Printer is OK. And in order to determine how warm your iMac is getting, download the free iStat Pro which will give you temperatures and fan speeds plus other items.

This White Screen is after the Gray Apple screen correct?

I agree with Chscag that the 2TB drive has nothing to do with the issue.

Did the Tech do a clean install of 10.6?

I am not sure if it was a "clean" install or not sorry, that is one thing that was mentioned by the techs who did diagnostic, that the OS might have a glitch...
I have installed the widget, and the highest temps are 54 degrees on the airport card, the GPU's...
So what next then?
(is it really called the white screen of death? - so that i can google it...)

To just add - When i can get it started it runs just fine, but is hot to the touch on the top, but not on the bottom... Also hotter at the top left of the screen.
However, when the screen has been asleep for a while the whole thing cools down quite considerably!

The iMac uses convection cooling, it is SUPPOSED to be very warm at the top and cool on the bottom -- that is perfectly normal, it's how the machine disperses heat (and why there's a slot in the back!). That has nothing to do with your issue.

I would guess that removing the tech's illegal install of 10.6 and replacing it with a clean, legal install from your purchased disk would solve the problem.

PS. Viruses?? HAHAHAHA that's funny.

And be interesting to know if this 'tech' was an Apple technician or not and what Apple would think of his free installing of Snow Leopard? You do have the original install discs, probably some form of OS X.5? Do as chas suggests, format the drive and do a clean install.

good

You guys are good!

BRIAN

I am doing a time machine back up now so that I can do another install of the OS, and yes it was an original disk, I have it here. However they have configured the formatting in a strange way and it says I can't do it because it isn't extended journaled.
So, doing the back up, then will have to take it back to them to fix I guess - do you think they formatted it a certain way to fit such a large hard drive in as has been suggested to me today by his offsider, or was it just done wrong and maybe this is the cause of the problems?
He is a mac tech of 15 years I understand, so I would hope he knows what he is doing