I've searched all over the web unsuccessfully for an answer to this question so I thought I would try here. The problem seems common but I've found no solution.

I recently purchased this motherboard (ASUS M2NC51-AR) used with hopes of building up a decent small form factor PC cheaply. Originally I guess it was in an HP slimline of some sort. I got it up and running using an old 1000 Hz AMD Sempron (tm) 3800+ w/256 kb cache. Now I want to upgrade the processor to something better, so I purchased an AMD Phenom x4 9100e. It is listed in the specs as compatible. However, after installing the processor when I turn on the PC nothing comes on the screen.

I have tried updating the BIOS. Previously it was v5.04, and now I am using v5.07. This required I first install Windows Vista which was a total pain. Currently I have two partitions, one with Vista and the other Ubuntu 10.04. I am wondering if there is another BIOS update (or other fix) to help the board identify the processor as compatible. Any help would be appreciated. Thanks.

depends on the site you go to but i find different cpu specs on different sites ,this one says it has duel core /athlon 64 .
http://www.algogo.com/store/products/ASUS-M2NC51%252dAR-HP-HematiteXL%252dGL8E-MINI-ITX-MOTHERBOARD.html

this one says what you say ,
http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00910076&lc=en&cc=us&dlc=en&product=3376325#N33

and many other links say only duel core as well,not quad core ,so not sure why but i would assume HP to be correct ,and it looks like bios 5.07 is latest .

the quad 9100e you bought is it new , or a used cpu

The CPU is new. I guess part of my question would be, is there another BIOS I can try out that is not suggested by HP? Perhaps something "open source." I am pretty ignorant on the BIOS other than to know it gets you to the boot menu.

The CPU is new. I guess part of my question would be, is there another BIOS I can try out that is not suggested by HP? Perhaps something "open source." I am pretty ignorant on the BIOS other than to know it gets you to the boot menu.

i know of none ,not sure where you would actually start looking for one ,and if you did use one and it was bad your board would/could be renders useless ,as the bios is the most important part of the motherboard