The Hindu scriptures also preached 'ONE GOD'

“Hinduism, as most Hindus would say, is not a religion but a "Dharma" and a Culture. The Vedas, the Upanishads, the Puranas, the Brahmanas Granth are considered to be the holy scriptures, most sacred being the Vedas. Also there is the Bhagavada Gita, the Mahabharata and the Ramanayan. 

The degeneration of any society starts with becoming heedless to the guidance of God and falling prey to our own whims and desires. This eventually may lead to the degeneration of the concept of God itself. The worship of innumerable Gods in Hindu society is a degeneration of the message of God and in stark contrast to the oneness of God preached in the Hindu Holy Scriptures Vedas and Upanishads. A few examples from these scriptures reveal that they also preach Oneness of God, which is exactly the same truth which was conveyed by God through His final messenger Muhammad (There is no god, but God).

• "There is only one God, worship Him" (Rig Veda, Vol. 6, Hymn 45 vs 16 )

• "Do not worship any one beside Him" (Rig Veda Bk. 8, Hymn 1, Vs 1)

• "God is only one, - not a second"- (Chandogya Upanishad Ch. 6, Sect. 2, verse 1).

• "na tasya pratima asti "There is no image of Him." [Yajurveda 32:3]

Consider the following expositions about the true concept of God from the Hindu scriptures.

• Concept of God in Hinduism by Dr. Zakir Naik

• On the Belief of the Hindus in God - Al Beruni (AD 1030)

• From the Islamic point of view, the message of Unity of God was being conveyed down through ages via chosen messengers to mankind. Allah says in the Holy Quran that each tribe was sent a messenger and a guide to convey this universal message of Unity of God. 

We thus invite our Hindu brethren to return to the worship of the One true God as reminded to us by God through His last and final messenger Muhammad (peace be upon him). The biggest injustice (which is also the biggest lie) which we humans can commit is to say that there are other gods as partners to the only One God. Proclaiming that there is no god besides the One God of all is what God wants to hear from us in words and deeds and this is the true step towards honesty and justice to ourselves and to society around us. 

The religion of the 'surrender to the one true God' - Islam, is the only path which God has chosen for mankind and is thus the only way to achieve brotherhood and unification of mankind and for salvation in the everlasting life after death. Worshipping others besides God does not please God, rather it is an act of disobedience to God and a sign of arrogance. By accepting this call of Islam, our Hindu brethren will only be returning to God's original religion for humanity, as we understand was also the original call of the Hindu dharma.”

http://saif_w.tripod.com/interfaith/hinduism.htm#OneGod