For a successful POST, you need a motherboard with power, processor and ram. Try removing all but those. Try clearing BIOS (this will clear all settings on motherboard, which may be a pain if you've spent a long time tweaking it, so try that last).
Did anything else unusual happen before this?
Also, what are the specs on that machine? Does the motherboard have onboard graphics? If so, were you using it? Removing all but the basics (as mentioned above) should at least let the machine post, but if you are using standalone graphics AND you don't have onboard video, then you won't be able to see any display.
Any caps that seem bulged or leaky? This is an issue that affects all sorts of electronics made with affected caps