You are confusing two types of memory. One memory is on your hard drives. Your programs and data are stored in that memory. Using A1Click and defragging can optimize the memory on the hard drives. It sounds like this is not the memory that you are referring to.
The other type of memory is RAM. It is the memory that handles what is currently open on your computer. For more information about RAM see my article on RAM at http://superwin.com/RaysComputerTips/Issue4.htm#computer
The easiest way to lessen the usage of RAM is to quit all programs that you are not using (Speed Startup can help by detecting programs started in the background that you may not know are running and getting rid of them). It is OK to use a lot of RAM (that is what it is there for, to be used) as long as you do not use it all or come close to using it all. When you do, things slow down and errors will occur.
Windows has a thing called virtual memory which helps free up RAM by moving some of the RAM to the harddrive. Virtual memory is slower than RAM but is only limited by the free space on your harddrive.
The numbers you give sound normal. If you want more RAM, you should buy more RAM and install it in your computer.
Programs have a memory footprint, the amount of RAM they need to run. The bigger a program is and the more a program does, the more RAM it needs. Programs that are poorly written also can use a lot of RAM. Cleaning and defragging will not lessen the amount of RAM used.
So your options are either to quit programs using up the RAM and run more efficient programs, or buy more RAM.