Problems installing a FX5900

Hi

Sorry this is a long post .. Ive tried to include as much relevant detail as
possible.

I have purchased a WinFast A350tdh FX5900 graphics card and this morning i
decided to fit it into my existing system:

MSI KT3 Ultra ARU, Athlon XP1700, 256mb PC2100, XP Pro (current card Radeon
8500)

I removed ATI's Catalyst drivers first and then fitted the card and
connected it to my PSU with the power cabling supplied. I then restarted my
sys. During the POST i normally get a message saying "Detecting IDE Devices"
followed by the options to press ESC to continue the boot sequence & CTRL-C
to setup my RAID. I always press ESC as ive never bothered with my RAID
capabilities. However - on this occasion when these options appear on screen
neither seems to work... And the boot-up process goes no further. I tried
several reboots (checking all connections etc) and the same thing occurs. So
i removed the FX5900 and put back my 8500. I left the FX supplied power
cables fitted tho. The system seemed to boot normally until the expected XP
Boot-up screen failed to appear and the sys just hung. I removed the new
power cables and rebooted the machine which booted normally.

So ... For some reason the FX card is causing my system to fail during the
POST. Could it be an AGP issue? As my board supports AGP x4 but the card is
AGP x8... Or perhaps a PSU issue? My PSU is a 300w unit.. Would the FX card
drain too much power from the supply to maintain motherboard integrity? (i
have 2 hard drives, a CD-R and a seperate DVD drive too) Or perhaps there is
a problem with the supplied cable? What about BIOS? Are there any settings
which may be causing a conflict? I havent flashed the BIOS as ive never
needed to ... If it aint broke then dont fix it is my motto!

Or are there some other factors which im unaware of?

Thanks for reading