HELP NEEDED TO CPU UPGRADE ON MSI KT3 ULTRA v1.0 (6380E.)

[newfy]

HI EVERYBODY !
I decided to upgrade the Duron Morgan core 1000Mhz to an Athlon xp 2400+ (2Ghz/fsb 133). According to msi website the KT3 ultra motherboard can support it. But my problem is that the new cpu is recognised as a 2800+ on default fsb 100, with a clock of 2250 Mhz.
The leds on diagnostic panel provided with the motherboard are all green (means ok), bios is reachable and can be modified, the boot seems to go well, winxp try to start but stop and bug even on safe mode. The same problem appeared on win98se. I tried to managed the right settings of the cpu through the bios (fsb 133 and ratio 15) but all led went red (wrong installed cpu or damaged cpu) and no answer from the computer.So i decided to go back on the Duron and the computer work fine again.
What does it mean?Did I miss anything on the upgrade?Is the Athlon damaged or not?Can anybody help please?
Note : I flashed the bios to the last version before changing cpu.