Thanks for the offer, it will be great if you can give some suggestions (brands, reasonable prices). I am not sure what are the range of prices for the portable hard drive, I remember I got mine for $100 but I got it from Dubia - I was not in the US at the time.
But I think there might be another culprit as well - my adapter. Earlier I got a message that my computer is slowing down and I need to change the adapter. I have also noticed that the battery takes very long to charge and it will not charge fully except when the computer is shut down and again it takes long. Even when the adapter is plugged, the computer keeps switching between battery and A/C power. So I am thinking I need to replace it as well! I don't think I have any other option that a Dell adapter.
Thanks for all the help!