Why moslems pray 5 times a day?

Its one of the five pillars of Islam.

1. Morning Prayer (Fajr).Two rakahs:

Begins about one hour and twenty minutes before sunrise and ends about ten minutes before sunrise. It is recited out loud

2. Noon Prayer (Zuhr). Four rakahs:

Begins when the sun passes the meridian and ends about two and a half hours afterwards. It is recited in silence

3. Afternoon Prayer (Asr). Four rakahs:

Begins from the time the noon prayer time ends and ends about 10 minutes before sunset. It is recited in silcence.

4. Sunset Prayer (Maghrib). Three rakahs:

Begins soon after sunset and ends before darkness approaches. The first two rakahs are recited out loud, and the third is recited in silence.

5. Night Prayer (Isha). Four rakahs:

Begins from the time the sunset prayer ends and extends till just before the morning prayer. The first two rakahs are recited out loud, and the last two recited in silence.

The five pillars are:

1. Shahada: testimony and declaration of faith.

2. Salah: prayer 5 times a day.

3. Zakat: percentage of salary to poor/charity

4. Saum: Fasting during Ramadan

5. Hajj: pilgrimage to mecca once in lifetime

source: (s)

http://www.dawanet.com/newmuslim/manual/description.asp