When a program is idle, windows moves the displayed program from memory to disk in a windows swap file (page file) which is supposed to improve machine performance. When the program is used again, windows tries to restore that program from thw windows swap file back to primary memory (RAM). This process of moving from the swap file to RAM is long delay you are encountering.
There are methods of increasing the speed from the swap file to RAM but the best method is to purchase a faster hard disk. A few years ago, hard disks that came with computers were usually 5400 rpm (revolutions per minute) and today the standard is becoming 7200. I suggest that you double it and get a hard disk that is 15400 rpm.
Regards to all,