Every open program's data must be stored in the system memory. As more applications are opened, that figure decreases. If the computer runs out of system memory, it will be forced to instead use hard drive space, which will cause the system to slow down and possibly lock-up. Being aware of how much memory is available is an ideal way to make sure the system isn't being over-tasked. No external programs or tools are needed for this task, since the operating system comes bundled with a tool called Task Manager that can measure memory usage.
Bring up Task Manager by holding down the "Ctrl" and "Shift" keys, then tapping the "Esc" key. Alternatively, Task Manager can be accessed by right-clicking on a blank area of the taskbar, then clicking "Task Manager."
Click on the Performance tab to view detailed system information. Locate the box titled "Physical Memory (K)," which can be found at the lower-right of the window. Three figures will be listed, "Total," "Available" and "System Cache." Each figure is measured in kilobytes.
Divide the number next to "Available" by 1,000 to convert it from kilobytes to megabytes. The final number will represent how many megabytes of memory are currently available. As programs are opened, closed and used, that amount will change dynamically. When tracking memory usage, it's helpful to check the available memory multiple times.