I have a HP Pentium III - 600 MHz Rev. HZ.01.10US computer that I need to upgrade both the HDs and memory. I have only a Maxtor 20 G HD and 256 SRAM with a Phoenix Bios 4.0 Release 6.0.c. I use The Shield Deluxe anti-virus . What is the maximum sized HD and memory that I can use to get this thing working again ? Its s-o-o-o slow !