Snow Leopard Memory Management Issues

I have a 13" mac book pro, 4gb ram, running snowleopard and have a memory management problem. After opening and closing programs, the "free" memory disappears and is replaced by more "inactive" memory and my systems slows to a crawl and is pretty much in inoperable until I restart. Even if I close every apparant program I still don't get me "free" memory back. I did some research on the issue and found others had the same issue and suggested things like turning off the "dynamic pager" and using the "purge" command. I tried the former, it worked for a while and then I started to get GUI glitches so I turned it back on. I'm looking into intalling the developer tools just so I can run the "purge" command but am feeling this can't be the proper modus operandi. Is there anything else I can try? Is there anything messed up with the OS that can be fixed? A common reply seems to be that the memory management is fine and nothing needs to be fixed. This obviously isn't the case for everyone! I have a macpro on Lion that doesn't have this issue, and when it was on Leopard, it didn't have the issue either, so I think this is situation specific. Any help would be appreciated, thanks!