I have recently bought a Sapphire 2600HD XT AGP card and as soon as its fitted the monitor does not get any signal. The fan starts spinning and i can hear the computer working but the monitor is just a black screen. I have tried to turn the monitor off and on but it just goes back to sleep.
 
I have bought a new power supply which never worked. I've completely ran out of ideas now and would really appreciate some advice.
 
Motherboard: ECS RS400-A
Processor: Intel Pentium 4 3.4
Ram: 2gig ddr2
Current GFX Card: Radeon 9800
Power supply: 550watt Corsair
 
I would appreciate some advice

Did you switch from onboard video to AGP in BIOS? Btw, why did you buy a AGP card? You should have gotten a PCIe since your board support it. That motherboard is one of those few hybrid mother boards:
http://www.pcstats.com/articleview.cfm?articleID=1789