Can I upgrade the processor for my Asus A7N8X motherboard? My current
processor is AMD Athlon(tm) XP 2100+ and if so what would be the next
in line to the top of the line?

Hello tmwes-ga,

Thank-you for your question.

You certainly can upgrade the processor on your Asus motherboard;
according to the Asus website the fastest CPU you can add is the
Athlon XP 3200+ (400 MHz FSB)(Model 10)(Barton).  Depending on how
up-to-date your motherboard is you may need to upgrade the BIOS to get
the motherboard to get it to identify the latest CPU's.

This information was taken from the latest ASUS website at:
http://support.asus.com/cpusupport/cpusupport.aspx?SLanguage=en-us&model=A7N8X

The link shows all the CPU's that can be used on the motherboard and
details of whether/how to upgrade the BIOS on your motherboard.

Should you require any further assistance on this matter please do not
hesitate to ask for clarification and I will do my best to respond
swiftly.

You can find out more about your motherboard here:
http://support.asus.com/download/download.aspx?SLanguage=en-us&model=A7N8X