Which OS is it? Try booting through DOS boot disk if u hv one. Try pressing Delete key during startup and see whether HDD is present. Did you change the RAM? If so, try starting your computer using the old RAM. If it starts, then the new RAM is incompatible with your mobo. Is any key stuck? Tighten everything on your mobo. CPU, RAM, Cables, GPU, Sound Card, etc. Inspect the power-supply connectors.
BTW, do u hv soln. for this thread?
Difference between these 2 HCL computers?