HP Compaq Presario,Presario 1515 Supplementary Manual page 12

To promote safety and comfort, follow these principles whenever you use your
computer.
Adjust your body position and your work equipment.
There is no one "right" position. Find your comfort
zone, as described in this Section, and when working at
your computer, frequently adjust within this zone.
Vary your tasks so that you can move around; avoid
sitting in one posture all day. Perform tasks that require
walking.
Build positive relationships at work and home. Relax
and strive to reduce sources of stress. Stay aware of
physical tension such as clenching your muscles and
shrugging your shoulders. Continually release tension.
Take frequent short breaks.
Listen to your body. Pay attention to any tension,
discomfort, or pain you may feel, and take immediate
action to relieve it.