Try FreeRAM XP Pro. It is free. You can get it here http://www.yourwaresolutions.com/software.html Also System Mechanic 6 has an option to optimize memory.
also...gime a sec here..ok..n/m...i wouldnt suggest gettin one..however..if u still want to try em..i'll post links to a few in a bit..
FreeRAM programs are sometimes useful after exitting programs made by bad programmers which leave stuff lingering in the memory. A simple reboot could do the job. It really depends on what you're doing. People who upgrade RAM either need it or are rich punks who just follow what others suggest without understanding why (Go lemmings!).
theres a really cool registry tweak and after you close a program, it unloads the DDLs and gives you back memory
Hey just go and buy more ram, they're not that expensive and i doubt memory optimizers are that effective. Just reboot ur comp sometimes if some stuff are taking up too much mb.