All 'decently programmed' programs return the resources they use if you close them. Only badly programmed programs take them and don't return them. The simple cure is to reboot.
The resources used by a program can't be influenced by the user. The only way to use less resources is to have less programs running. The ways to go:
- Remove unnecessary programs from your start-up list (using msconfig); be sure you know what you do, however.
- Scan for spyware.
- Close programs and windows you don't need any more.
Hope this helps.
Kees
how can I make windows 98 return resources after I've closed several programs, and how can I make it not to use all the resources?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic