not much possibility at all... except at a highly unreasonable cost. The board is limited on the processor it can use, and on the amount of memory that can be installed. It is not the cpu at 1.33 GHz that limits you. It is the front side bus. Thje maximum CPU that can be installed, according to my Presario manual is 1.47 Ghz... not a lot of increase from the 1.33... about .14 Ghz
As you have already learned, 624 mb of memory is not much.
You can remove the screen if you have the tools and the schematic, but be extremely careful as the ribbon cable is extremely brittle and can shatter at the very small pressure pressure or tug.
The hard drive can be upgraded from a 4200 rpm to a 7200 rpm. That will help great deal for about $75.
You are also limited by the TFT display which cannot be changed.
All the specs for the computer are available at
www.hp.com.
An additional problem is that it has a history of the screen failing early under normal conditions. You risk the screen failing eve earlier.
Much less money to buy a new or refub one designed for speed... and not a presario... more like an HP, Dell Latitude or Inspiron, Gateway or IBM Lenovo Thinkpad... something with 2 GB of memory potential, fast hard drive, fast frontside bus, and better screen with independent graphics card.