Which is the best suitable operating system for my pc

_RoRo_

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Dec 18, 2010
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Gaming -> a flavor of Windows (XP if low on RAM, Win 7 if more than 2G of RAM)
Anything else -> Ubuntu or another flavor of Linux, Ubuntu is very user friendly though

Be warned though that Ubuntu might require some tinkering to get working and from your question it seems that you're not really computer-savvy.
Hence my overall recommendation is the first line =)