I used to use Memturbo .. it seems to be quite a resource hog on its own, but it does help you from memory crashes if you are very low on resources (< 60% on system properties) if you keep flushing it. I've noticed if I flush my memory regularly , I would have to reboot once every 2 or 3 days, instead of once every 4 hours.
I can't say it's a great software or anything, but if you have serious memory leaks with your software (doesn't free up used memory after you quit the program, for instance) , then it could help on a temporary basis. Best bet is to run a modern OS system and get 256+ megs of ram