black screen when start up, and can't shut down

[idler]

After i plug in and plug out the two harddisks, then restart, the computer can't be startup when i press the power button of the case. After i've changed the power colt, i can startup the computer by pressing the power button, but i keep pressing the power button for a long time, the computer can't be shut down.

Which part of the computer hardware most likely cause the problem?

[patio]

1st culprit...Power switch.
2nd culprit...the PSU itself.

But why are you plugging and unplugging the HDD's to diagnose a power issue ?
Reason i ask is i've seen the BIOS get temporarily cornfused when drives are constantly being unplugged, re-jumpered and dis-connected...

[idler]

@patio
The reason's i plugging and unplugging the HDD's is to install window 8 for my main harddisk, after installed, i plug back the harddisk, then the problems occur.

The strange is that the case front fan is also stopped. Maybe it really the power switch problem.

[patio]

Nope...now the PSU has moved up to #1...
That or the front header wiring itself...

P.S...are you saying you are installing Win8 on a different PC...then swapping it to this one ? ?
"Cause that'll never work.

[idler]

Same pc, i have 3 harddisks

[patio]

The reason's i plugging and unplugging the HDD's is to install window 8 for my main harddisk, after installed, i plug back the harddisk, then the problems occur.

Then clarify this please...'cause i'm overlooking something...

[idler]

What is the main reason i can't shut down the computer when i Press and hold the power button? it is strange.

[patio]

I still don't get it...probably due to a lack of details...installing any Win version does not require a power down or cold boot...  re-boot yes...but it does that on it's own...
Someone else will be along shortly...

[idler]

The installation of win 8 is successful, After that, i close the window 8 and my computer then open the case and plug back the unplugged harddisk. Then the computer can't be started.