I did some searching (as time permitted) and it sounds like this motherboard is problematic with Linux. Many of the posts I saw were old, dating back to 2005-2006.
However, I did run across this more recent link, which might be helpful:http://que-cosas.blogspot.com/2010/01/instalar-ubuntu-910-con-placa-base.html
"Instalar Ubuntu 9.10 con placa base ASRock P4i65GV
." ['Installing Ubuntu 9.10 on an ASRock P4i65GV motherboard'] 22 Jan. 2010.
The OP indicates that there is a compatibility problem with the AGP graphics card, so the solution is to disable it in the BIOS settings before attempting to run a Live Linux CD and perform an installation.
He does note that the GeForce GPU does not work, if you try to use it following your Linux install. (I don't know if that might have been remedied with more recent Linux kernels ...)
If you don't read Spanish, you could run this through Google Translate. (I did not have time to read through all the comments):http://translate.google.com/