Almost all the time, I end up with no memory available and the system halted. At the beginning, memory is not a problem. As time goes on, allocated memory increases even if I do not generate new variables. For example, I keep using 'print' or 'help'. Finally no free memory is available. When I run a huge program unknowingly, the system halts. Also windows multi-tasking becomes impossible. Why does this happen? I am using IDL 5.4 on Pentium III 700 MHz, 392 M RAM, 6Gb HDD.