It is easy to understand how the idea of Muslims praying five mandatory prayers a day is misunderstood to mean that they pray only those five observances and no more. The key word here is mandatory. The use of prayer in many individuals' lives, though they belong to varying faiths, is done when they need something, in gratitude, in times of trouble and other times just to commune with God. Muslims pray for those reasons as well. Those opportunities for prayer beyond the five daily prayers are known as dua.
Why the fardh prayers?
The goal in observing the mandatory, or fardh prayers is to achieve a mind of celebration. It's not intended to approach prayer with a mindset of drudgery or obligation but gratitude and joy that one is able to do so. The ayah, or verse, quoted below is exemplary of the mindset one should have when approaching prayer:
Ta-Ha 20:130 "... and celebrate (constantly) the praises of thy Lord, before the rising of the sun, and before its setting; yea, celebrate them for part of the hours of the night, and at the sides of the day: that thou mayest have (spiritual) joy."
The prayers made by Muslims are believed bring them closer to God. Not just at night before bed or over meals, or when the spirit moves them, but five times a day. A Muslim detaches himself or herself from the daily demands on time, the worldly obligations and tasks one must fulfill, and halal, or permitted pleasures in one's daily life at specific times of day so one is able to recall to mind God and the things of God and those qualities of God one would like to emulate to the extent that the individual Muslim deems his or herself humanly able. The Muslim approaches an unseen, though seen, all powerful and singular God in the state of humility. Humility, because they believe and know that all they have and all they are is by the will of God alone. It is deeply believed by all practicing Muslims that God alone can meet their daily needs for food, shelter, family, success, etc. in their day-to-day lives.
Muslims pray the Fajr, or morning prayer just before sunrise. This is the shortest of the prayers. It contains only two raka. A raka is a complete cycle of prostrating (sujuud), bowing (ruku), and standing.
The longest prayers of the day are Dhuhr, Asr, and Isha. They consist of four raka. The first two are performed throughout the day, the latter is performed in the late evening after Magrhib and before the Fajr prayer. The Maghrib, or sunset prayer, is said as you would guess, at sunset and is the only prayer with an odd number of raka, three.
The Fajr and Maghrib prayers are performed at the time when two of the most awesome natural phenomena occur, sunrise and sunset. The change of day to night and night to day can be executed by non other than God and he has set this in motion to occur like clockwork. In contemplating this one is at once awed and humbled by his power and wisdom.
So, yes, Muslims do pray five times a day; joyfully, and willingly. In these prayers they seek to demonstrate their obedience to God and display their gratitude for all he has given them. Muslims are not limited to those five daily prayers, but those are the only prayers that they perform (except a few special prayers to be covered later). At key points during the day Muslims are reminded of God and Islam and they also set aside their daily tasks for that which has a higher priorty in this life.
Find out more in this demonstration about how Muslim prayer is done.