basic difference between i5 and i7 processors?

The big difference is Hyper-threading.

If you do not use a lot of "Threaded" applications which take advantage of this then get an i5 and save some cash.

Hyper-threading usually boosts the performance by around 20% if all threads are being used. At the moment unless your running lots of applications at once, doing large image processing through a program like Photoshop or video encoding then there would be little advantage in buying an i7 over an i5.

It might be worth investing more money in getting a faster (GHz) i5 than a slower (GHz) i7 :)

edit: overheating is not something to worry about in this case as and i5 or i7 with stock coolers run pretty cool.

The i5 is of decent speed and value, if the i7 is a considerable amount more than the i5 then I'd go for the i5.

The i7 is usually a Quad core, split into 8 threads. This uses something called hyperthreading technology.

I have a i7 Laptop and even though it is very fast, I can think I can do with an i5 instead.

Hope I've helped.