Slow Compaq

Just got done working on a Compaq of the following description:
Compaq Evo D300 Desktop Series
Evo D310v Model with Intel 845G Chipset
1.8-GHz with 400-MHz Front Side Bus
Has 128-MB DDR Synch Dram PC2100 (266-MHz) Non ECC

Operating system is XP-Pro.
It was slow to start with. No updates had been done. I updated it to SP1
and installed the rest of the critical updates. Norton was up to date. I
did a full system scan... it was clean. Found a moderate amount of adware
and spyware and removed it all. Only 5 items checked in Msconfig... all
normal stuff. Task Manager doesn't show anything unusual running. It is
*still* slow. I have a 850 Mhz machine of my own (one I built) that will
run circles around this one.
Dunno why it shipped with only 128 Mb ram and I have ordered another 128
for it, but I don't really look for that to speed it up much.
I didn't look in bios but these days there's not much you can change and I
don't want to make it unstable.
Is this just the nature of the beast?

--
I child-proofed my house but they are still getting in.