Thanks for your reply buzznut.
To update some information:
Original system: HP Pavilion a6152n
Quote:
Core 2 Quad Q6600 (K) 2.4 GHz
1066 MHz front side bus
Socket 775
Chipset
Intel G33 Express
Motherboard
Manufacturer: Asus
Motherboard Name: IPIBL-LA
HP/Compaq motherboard name: Berkeley-GL8E
Memory
Memory Installed 3 GB
Speed supported PC2-5300 MB/sec
Type 240 pin, DDR2 SDRAM
Hard drive
400 GB SATA 3G (3.0 Gb/sec)
7200 rpm
16X DVD(+/-)R/RW 12X RAM (+/-)R DL LightScribe SATA drive
I bought an ASUS P5G41C-M LX motherboard and new HDD (1TB) and swapped over the CPU, RAM, DVD-RW drive and PSU. When I got it all together, I plugged it in and absolutely nothing happened, just like before. So, believing it was then the PSU, I bought a Corsair 400W PSU. I swapped the Corsair PSU in, hooked it all back up and it booted into the BIOS. I was too slow to hit the DEL to actually get into BIOS, so I was stuck in a loop asking for something I can't recall now. So I powered it down, rebooted and hit DEL into BIOS. I set it to boot from the DVD-RW drive, inserted my Ubuntu disc, and Save/Exit BIOS. Ubuntu started fine, and I started the process to load the OS. I got a few questions in when it suddenly shut off.
Now, after posting the OP wondering about a bad CPU, I took the Corsair PSU out, and swapped it into this computer (the one I'm online with right now). It spun the CPU and Case fans for a millisecond, then nothing.
The two computers are set up on different outlets and different surge protectors. The original surge protector is aging, and I'm now wondering if that is the problem - that it zapped the old PSU, and then when I plugged the new one in to the old cord that was still in the old surge protector, it zapped that one.
Also, to note, the original HP PSU has a LED light on the back of it. It would come on when the 24-pin connector was disconnected form the motherboard, and both motherboards connected to the Corsair PSU had their lights come on, but still not do anything.
Sorry, I know I'm a bit all over the place - I hope you all can make heads or tails of it....