I think you are in luck.
If you go to Asus site you can look up the cpu support of the motherboards, for example
here ....it doesnt SPECIFICALLY show your "AM" model but it shows about 6 or 8 different "CUW" models and they all support on up to faster celerons and also all showed support for P3's. So that gives you some upgrade room right there. You might even consider a used P3 from somewhere like
www.anandtech.com sale/trade forum.
Another option is to use one of
these adapters that allows the use of a "Tualatin" celeron or P3. What you would usually do is get a tualatin celeron since they are fairly cheap and are better than the much higher prices 'coppermine" P3's. You can get a new Tualitan 1.2g for like $42 dollars or so from newegg. If you scroll to the bottom of that adapter page you see a link for
this page showing again the range of 'CUW" boards but not specifically the "AM"....so I dont know if that would make any difference or not. I have used these type of adapters before and they work good...sometimes you do need a particular bios to get em to work.
By the way they also make better power supplies now for those micro-atx sized deals. You can get those from newegg also...like 200w or so to replace the 145w (or less, lol) stock one.
Here is a place that sells updates bioses...not that Id recommend that necesarily, but they did have some info about the motherboard...I also found out it is called a "tortuga" board...one of those weird nicknames...it is an asus board specially made for HP
JP