My system specs are:

- Processor: Core 2 Duo
- Motherboard: ASUS P5g41t-m LX
- GPU: Nvidia 9500 GT
- HDD1: WD 500 GB SATA
- HDD2: WD 500 GB SATA
- Optical drive: Samsung DVD RW
- Power Supply: Some unbranded one that claims on its label it's 700W which I seriously doubt.

I have Windows 7 64 bit in HDD1 and OS X Lion in HDD 2 that I installed using Hackintosh distro. I press F8 key on POST screen which gives boot drive selection menu from where I select the HDD to boot from.

The system was running flawless on both operating systems until recently. The problems are listed below:

- Almost always it takes unusually long for POST screen to appear (around 60 to 90 seconds) whereas during good condition it used to appear within 5 to 10 seconds of power on
- Sometimes the system doesn't receive display signal
- If I take out power cables from all SATA drives but one, then the POST screen usually appears normally for sometime.
- At one time I removed ALL SATA drives, i.e. both HDDs and DVD then turned on, it turned on promptly without delay. Then I connected Optical drive and turned on, it turned on properly. Then connected the HDDs one by one, and it still turned on without delay. But this lasted only for 2 days after which the same problem, i.e, either POST screen appears after painfully long time or doesn't appear at all

Before this motherboard, I had Intel DG43NB and had both Os X and Win 7 and experienced exactly the same problem and my hardware guy told me that my motherboard had gone down so I replaced with this ASUS one. Again the same problem with this board

My questions:

- Where is the problem?
- Could the problem possibly be in the motherboard? I think it's unlikely because once the system starts it works flawlessly, i.e. no errors, no crashes, nothing.
- Could it be the power supply? Since it seems to work better with less load, i.e. some drives disconnected.
- Could it be the GPU?
- What's the best way to diagnose?
- Does the problem have anything to do with my frequently switching boot drive from POST startup menu?

Any help will be greatly appreciated since I am in the middle of an important project and I dread the day when I am not able to turn my machine on at all.