I agree. Do not worry about it, a standard ATX should fit. Why not call India and have Dell do warranty on your computer over a 1-900 line
Anyways I'd get a new PSU. Even if that's not the problem, you want a good PSU. The most important part of any computer is a quality power supply, not the CPU speed like most people believe. The standard DELL ones are crap. The Antec mentioned above is fine, or even upgrading to an Antec NEO with modular cables is even nicer.