Hardisk/Power supply failure HELP !!!!

[damchey]

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Hi,
Lately my computer couldnt not boot up/power on.Below are the details of my computer problem.
I have a Seagate baracudda 7200RPM 80GB harddisk and an 300W power supply. I havent used my computer for about 4 months as i was away from home, in that time, i had removed my harddisk and taken away with me.
last night i connected the harddisk and switched on my power, and the computer worked fine.
So i finished setting up the computer and then, i figured that i didnt connect the cd drive IDE cables. So i again opened my case and refitted all, but then, the computer wont power on.
Only when i remove the power supply cable from the harddisk , will the computer switch on. So i couldnt get my PC to work.When i insert the power cable into the harddisk, the PC wouldnt turn on at all. Not even a flicker of light at the LEDs.
So i am confused, what did i do to cause this problem. Is it a problem with my harddisk or with the power supply not being able cope up or something like that.
Please help.
And if its a problem with the harddisk, can i get it repaired, i have loads of data in it. Just dont want to get them all erased.
Please help.

Thanks

 

[damchey]

Brand of PSU is INTEX(its an indian Brand). It was working perfect for over a year now. I think the problem is with the hard disk. When i remove the power cables from the hard disk, the PC boots up fine, but no OS.
And also i forgot to mention that, while connecting the harddisk after the refitting, when i plugged in the power cables to the hard disk, i saw a small smoke come out of the power socket in the hard disk.