To my knowledge they do not work and should really not be used. The best way to actually clear ram is by doing this
Open up Notepad (Start, Run, "notepad" (OK)). Then put this in
Mystring = (80000000)
Save it as "Memory.vbe" (including the quotes!). Close as many programs as you can, then run (double click) this handy little script to free your memory whenever your computer is feeling sluggish.
If you have trouble running it, you may need the Visual Basic Runtimes.
This helps after games especially because there is alot of stuff leftover in ram