A friend of mine has a HP pavillion 700 that just won't boot. When I turn it on, it won't post and the monitor isn't getting any type of signal. The system is an Athlon XP, ASUS A7N8X-LA MB with 256 MB PC2700 RAM, built in audio, video & LAN. When I power it up there is no beeping from the MB, but I am able to hear the fans & hard drive.

I've tried the following (in no particular order):

1.) Replacing the motherboard.
2.) Replacing the power supply.
3.) Replacing the RAM.
4.) Replacing the hard drive
5.) Resetting the CMOS & replacing the battery.
6.) Using an AGP video card that I know is good.

The only thing I can think of that I haven't tried yet is replacing the CPU. If that isn't the problem, is there something I haven't thought of doing that could be causing the problem?

The CPU was the problem. Got one off E-bay, installed it today and all is well.