It's usually a bad idea to use a windows application to overclock. Overclocking is usually done from within the BIOS. I believe the i5's are the same as an i7, to get to a slightly higher clock(3.2 or so) not much usually needs to be done, just raise the core clock a little. When you start getting into higher clocks(usually around 3.5 and beyond) you will need to raise the core voltage. This is where you can fry your CPU. Never mess with the voltages if you don't know what you are doing.
Like dipankar said, if you are seeing no slow downs on games ect, you probably aren't going to notice much difference. Synthetic tests are just that, synthetic. But if you are like me and can't help but tinker, then by all means, go for it:) Go to this link, it's an overclocking guide.http://www.tomshardware.com/forum/256144-29-1156-core-overclocking-guide]