After 12 hours of worry and planning contingencies on the PC upgrade, I came home and tried booting with my old AGP card. The display is back! I re-inserted the new AGP card, no display. The verdict is out: fault is on the new AGP card. Tomorrow I'm heading back to Sim Lim once more in hope to get a 1-to-1 replacement. Having patronised the shop for 4 years, I do hope they don't disappoint me.