Workplace Angel
Workplace Angel reminds to make pauses in your work and helps to adjust workplace for comfortable and healthy working. It helps you to prevent computer-caused diseases such as musculoskeletal disorders (Repetitive Strain Injury, Carpal tunnel syndrome, Tarsal tunnel syndrome, Sciatica and... Program can be used as a health care solution for companies. ... Workplace Angel also allows to set daily and weekly computer usage time limits.
http://www.wpangel.com/wpangel.exe - 2Mb - Download - Screenshot

Healthy Work
Do you ever get aching muscles and stiff joints from sitting in front of your computer too long. A team of health care and ergonomics specialists developed Healthy Work to increase circulation, relieve tension, and help guard against Repetitive Stress Injuries (RSIs) such as Carpal Tunnel Syndrome. ... The key to this is pacing your work - maintaining an even work rate, taking regular breaks before fatigue occurs, and doing stretches and exercises to rejuvenate your muscles. ... Healthy Work is intended to stop you from getting sore eyes or aches and pains from using a computer.
http://www.winshare.com/download/hw30.exe - 0b - Download - Screenshot

UsefulRest
Protect yourself from excessive computer use. With permanent and long-term computer work, you are vulnerable to eyesight deterioration, back and hand pain, headaches and eye problems. Why endure this needless stress? In order to prevent these potential problems, most ergonomic experts advise... This software has an inexpensive solution to compel you, your fellow workers, children, and other loved ones to take that much-needed break. ... With this software, you can program your computer to freeze when you want for periods up to fifteen minutes per hour.
http://www.olympsoft.com/download/usefulrestsetup.exe - 1Mb - Download - Screenshot