its 3.0 Ghz pentuim dual-core, i think the motherboard model is gigabyte but im not sure, 4 512mb memory cards making it 2gb ram, graphics card is manli geforce gt 430 2gb ddr3, psu is 500w... hope this is helpful.
Is this a recent problem as in it worked before but has stopped working recently? Have you changed anything internally or externally (cables etc). Could really do with the motherboard model number. You can get this from CPU-Z which will give you the details. Also the make and model of PSU woulde be really helpful but this will involve opening the case if you no longer have the box.
the problem started when i connected another sata hard disk drive into the motherboard. Im suspecting that my hard disk has been corrupted but how can i format it if i cant get any display? The PSU make and model is written in Chinese because its made in China. Is the motherboard model number also written on the motherboard? Im using another CPU right now.
If all that changed is adding an extra HDD, you could try unplugging the extra HDD's power cable and see if the PC boots. If it does then either the PSU is a piece of crap that cannot handle the extra ~20W to spin up the extra drive or the drive is defective and causes your PC to crash on POST.
Unless you live in/near China, I would be quite suspicious about a PSU so generic that the company did not even bother putting English labeling on it.
If you have put a new HDD in try what invalidError has said as it could either be the PSU (generic ones can be nightmares for inconsistent power output) but it could also be a boot device issue although I suspect it would throw up some errors on start up.
I have removed the extra HDD and it worked fine except the administrator blocked the Windows Task Manager. The next time I turned the computer on, there was no longer any display. Monitor shows "no signal" message.
Looks like the extra HDD pushed your PSU over the edge and now the PSU is in its death spiral.
This is often due to leaking output filter caps inside the PSU and can be fixed with ~$5 worth of parts if you are handy with soldering iron and picking/ordering replacement capacitors or know someone who is. Otherwise, time for a new, preferably better PSU.