it keeps the ram memory free
Yeah, you probably mean it tries to maximize the amount of free pages in the physical memory, which is a bad thing.
The memory management of Windows 2000k and later is good enough. If you have problems with some programs then it's probably a memory leak in one of those programs, or you have not a lot of RAM anyway... 512 MB is a minimum on Windows XP and older... it's better to have 1GB.
And Vista needs at least 1-2GB.
DDR2 RAM is cheap at the moment, older DDR is very expensive (twice as DDR2)...
so if you have a newer system buy more RAM if you're underneath the values above.