Upgraded Processor, windows wouldn't load, tried Xp disc BSOD everytime setup starts

[EsquireCC]

Hi Folks,
I hope someone can help me out as this is a new one to me.
Here is my origonal system:
AMD 64 Clawhammer Skt 939 3000+
1.5 gb ram Geil running dual channel
ECS KN1 motherboard
Radeon x850pe Pci-x
100gb sata hd

My system was working fine, has windows XP pro SP2 installed on it (my xp pro disc is a SP2 copy) no issues.
Bought brand new processor
AMD 64 skt 939 3500+ Venice core
Installed, cleared bios and resetup. Got windows XP logo and then an error saying my system32 was corrupt to insert xp disc and do a repair option.
So I tried.
Now computer gets as far as loading Xp setup and Setup is loading windows and then I get BSOD
I've had a couple different errors:
they are all Stop: 0x0000007E errors
PCI.sys and Isapnp.sys are the two that keep coming up.
Any suggestions?

Thanks
Daryl