• As you go about your normal computer tasks, each program you run uses a certain portion of your computer's memory. When these programs are closed, it is not uncommon for fragments of this memory to continue being used, even though the computer has long since gotten rid of whatever was using them. Memory consumption like this can eventually cause slowdowns and system failures, so it is advisable to clean your memory out every now and then to keep everything running smoothly.
  
  

Vasilios CleanMem 7.20 (Freeware)

• Vasilios CleanMem is a Windows memory utility (compatible with XP) that was designed to assist users in reducing the memory impact of the software they use. The program will scan through your computer memory to get rid of fragmented data and pages, as well as reduce your running processes to their bare minimum to ensure everything is running as smoothly as possible. It also includes a real-time memory tracker that runs on your Windows taskbar.
  
  

PCWinTech: CleanMem v.1.5.1 (Freeware)

• This program is similar to Vasilios CleanMem in that it helps monitor your processes and cleans up errant memory tasks through your system, but it also cleans out your system cache (a major source of software slowdown). If you find that your computer mostly experiences slowdown issues after running complex tasks or playing video games, the system cache may be the culprit.
  
  

PointStone: MemOptimizer 3

• MemOptimizer runs through your system processes and actively manages your system memory to keep your computer running efficiently. It automatically clears a lot of the memory issues that occur as your open and close new programs, and comes complete with an active memory monitor that updates you in real time about your memory use. The main difference between this program ($19.95 as of October 2010) and the freeware options is that MemOptimizer is focused on monitoring memory issues as well as cleaning them.