Hi Moff, Welcome to Techimo!
First you will need to find out what you have now.
Choose Start, Settings, and Control Panel.
Double-click System icon.
Choose the General tab. The processor type is listed on the lower right side.
Depending on your results You may/may not be able to upgrade.
List of all upgradeable cpus within its socket class(each socket is incompatable with another socket class)
Super Socket 7
AMD K6-2 500 (cant upgrade)
Socket 370
Intel Celeron 500, 533
Intel Pentium III
Intel Pentium III 533/133
Intel Pentium III 550/100
Intel Pentium III 600/100 or 133
Intel Pentium III 700/100
Intel Pentium III 800/100
Slot 1
Intel Pentium III 600/100 or 133
Intel Pentium III 667/133
Intel Pentium III 800/100 or 133
Slot A
AMD Athlon 700
AMD Athlon 800
From here:
http://h20000.www2.hp.com/bizsupport...odTypeId=12454