Whenever you change any connections or cards or ram etc. inside your computer case, you must REMOVE the power to the case. ATX mboards are always powered some places, including some contacts in the ram and video slots, even when Windows is Shut Down or in Standby or Hibernate modes. If you don't remove the power to your case, you can damage ram or cards while installing or removing them, or damage other comonents connected to your mboard including the power supply.
Did you change what ram you had installed, or change the positions it was installed in, before you changed the video card the first time? If you didn't, and/or if you didn't fiddle with the ram at all, it is extremely unlikely the ram is defective (or in the wrong slots), unless it has been damaged by something external such as your power supply has gone wonky and is producing voltages that are too high, or your computer has been exposed to an AC voltage spike or surge since it last worked properly and your computer and everything connected to it is not protected against that.
Failing power supplies are the most common cause of symptoms like yours and will often partially work but not allow the computer to boot fully. See the link in response 2 and check your power supply.
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If you DID change what ram you had installed at the time you installed the first video card, and you used ram modules you haven't used in this mboard before, yes, it's possible for that to cause problems if the ram is not compatible with the mboard, but usually if that's the case, either at least some of the ram is not recognized properly but the computer works anyway, or in the worst cases the computer won't boot at all - it may not even give you an error beep.
If you DID change what ram you have installed, change it back to way it was when the computer worked properly if you can remember which modules and where they were installed, or if you can't remember, try one ram module at a time, assuming at least one is what worked fine before.
As far as whether it makes a difference which slots you have the ram installed in, and if your mboard can use more than one type of ram which slots it must be installed in, see your mboard manual.
"....i was reading some reviews of owners of the mobo n they were saying its picky with the RAM...."
You have to make sure the ram is compatible with your mboard if you haven't had it installed and working fine in the mboard before. Randomly trying ram is a crap shoot. If the ram you had installed worked fine previously in this mboard, there's probably nothing wrong with it.
See response 5 in this for more info about ram compatibilty, and places where you can find out what will work in your mboard for sure:
http://www.computing.net/hardware/w...
