Is thermal past a MUST?

The heatsink that came with your i5 should have thermal grease on it already, if it does not DO NOT run the system until you get some thermal paste between the CPU and heatsink. The CPU will heat up very fast and possibly damage itself.

i strongly suggest thermal paste if you don't want to risk damage to the CPU. you can grab a tube at radio shack, staples, best buy, etc.,

Thanks.. I'm using the stock cooler/fan though for now to save myself some money..and thre is three stripes on the bottom of it. I believe thats thermal paste, no? I won't be overclocking or anything..at least not for a while. I read on another forum that it was fine to just stick on the cpu and fan with the paste that already comes on it... yes? no?

Stock fans if its new will have the thermal paste on it. The paste that comes on it is fine for stock use but if you do want to overclock I would recommend getting an after market cooler and use quality paste.

If you do remove the heatsink at some point in the future you will have to clean off the old paste and reapply new paste.

Yep! thermal paste it's always a good idea lol!

Short answer: yes
Long answer: Unless you want to replace parts, then you better put some on, but make sure that your stock fans dont already have some.
Too much is as bad as not enough.
Researched answer:
I have read about companies developing "thermal gel" for CPUs.
This gel works the same way, by transfering heat with suspended metal particals, but is different to the hard mostly metallic compound we have come to love.
Directed to your response:
You said there was 3 strips of thermal paste?
It is best to evenly spread thermal paste to insure consistant thermal transfer. More surface area of the paste to the CPU fan/heatsink will allow for better cooling.
I hope this helps!

Hi..sorry for the delay in reply. As for my CPU..there was already some there by the manufactuer on the stock fan. I don't plan on OCing anytime soon so I just went with that.

I do have a friend though who's system is running extremely hot, especially the video card. I was going to pick up some thermal compound. Is the metal-based or silicon-based the better one? I've heard the metal one is better.

Also, can I use the same thermal paste on the video card as I use on the CPU? I've never re applied it to a video card before so was hoping if someone could give me a few pointers on that. I don't even really know how to go about re applying it on a video card..but I know you can on certain ones. So whats the best to use? Thanks!