The issue of memory management was not resolved. You also may find the an application such as a firewall will leak memory.
The "why?" is simple. Programs you are running are leaking. You get to find the leak. I must ask why you are running Zone Alarm. It does leak on every machine 98/ME I've found and we can discuss what it's saving the machine from.
My machine is an e-machine with a 667 mhz processor. I have 256 mb ram, 40 GB hard disk. I am running SBC DSL. I have noticed that my available ram continues to diminish as I operate programs. It starts out at about 67% on reboot. I have only critical programs loading on startup (Zone Alarm, antivirus, sound, Adaptec cd creator, Lexmark printer.) The available ram slowly diminishes to about only 45% (with no programs activly running) after about 3 days. Why does this happen?