Hardware changes resulting in no boot

Hi,

I've tried to make some hardware changes in my computer. I changed the graphic card to a crossfire system, added a new hard drive, add 4 GB RAM and removed my old floppy drive. Then I connect it with a display, and it starts and I can hear that it searches for windows on first the disk drive and then the hard drive but I get no output on the screen... Okay, then I removed the new graphic cards and put the old one back in. Still no output... Then I changed it all back, to what it was, and still no output? What could be wrong ?
I probably should mention that the display I was testing it on were not my standard display, but an old Fujitsu-Siemens display, but still a VGA flat screen. I tested the display by connecting it to my laptop and it worked fine.


Old specs:
MSI K9A2 motherboard
AMD Athlon 64 X2 6000+ 3,1 GHZ
Sapphire Radeon 3850 512 MB
4 GB RAM Kingston
Maxfactor(or something) harddrive 250 GB
Harddrive 80 GB
A DVD, a CD and a floppy drive.


New specs:
MSI K9A2 motherboard
AMD Athlon 64 X2 6000+ 3,1 GHZ
2 x Sapphire Radeon 6950 dirt edition in crossfire
8 GB RAM Kingston (not exactly the same as the old ones, but they fit ? )
No floppy drive and added a 1 TB Seagate Barracuda 7200.12


Hope you can help!! :)