Yes, the total of the memory used by the processes listed should roughly tally with the the figure shown on the performance tab.
And that isn't the case, if I am right.
If it does not, then this would suggest that there are some hidden processes running on your system.
How could I make the hidden processes visible? And may be stop / delete them?
Also because the number of processes you have running requires more physical memory than is available, it means that the system needs to be continually reading and writing to the paging file, which will slow down your system.
Yes, how many RAM must be free / unused, to let Win run properly? So, may be using 3 GB (of 4 GB available overall) is good. Or can you use 3,9 GB RAM without loss of performance. Sometimes the TM shows about 3,5 GB RAM in use and the system runsextremely slow, sometime the system runs not that so, though the same amount of used GB is shown. Why is it like that?
May I suggest that you try having fewer programs running at any one time to see if that helps with system performance.
Yes, thank you, but it is not possible actually. There is no program I wanted to miss. I had thought about already, but...